IMO this game is still pretty new and doesn't need major overhauling. As someone invested in a pretty high tier character, I have real insecurities. Upon thought, if I had the power to make this patch myself, here's what I would do...
Diddy Kong:
Uair should kill about 20% later,
IASA on both dthrow and uthrow moved 1-2 frames later (but same launch angles and such).
Monkey Flip (default only) and fair minor damage nerfs (like 1-2% less damage on each).
Otherwise no changes.
~Diddy isn't as problematic as some people say, but the game is better if his throws are not super guaranteed and instead merely sometimes guaranteed but always very good chases. Uair is just ridiculous as it stands. Monkey Flip and fair are wonky in how hard they hit, and that too imbalances the character. The above Diddy is likely still high tier if not still top, just not as "clear #1" as he is now.
Sheik:
Slightly more endlag on both default and piercing needles.
Otherwise no changes.
~Sheik is better designed and balanced than she gets credit for, but one aspect that isn't really good is how she can needle camp out slower characters. Making them a bit less safe would let the bigs approach her a lot more viably while not taking away from the stuff about her game that makes her such a valuable part of the game's design.
Rosalina:
If Rosalina is not free to act, Luma can no longer chain jabs
Rosalina should have to mash a little harder to get rapid jab (quality of life change, not for balance)
Both character uairs should kill very slightly later (about 10% later on average)
Rosalina's nair (not Luma's) should have slightly bigger hitboxes.
Fair should have about 1 frame less landing lag.
Otherwise no changes.
~I don't think Rosalina needs a substantial net nerf; she was already nerfed really hard in 3ds. She is, however, really good, and her uair is part of what's just kinda dumb about her though you can't nerf it very much or you risk ruining the character. A little nerf would be fine though and probably for the better. The jab chaining when in hitstun or grabbed is honestly stupid and causes bad player experiences without even helping Rosa that much. On the other hand, seriously, it's just obnoxious how easy it is to accidentally rapid jab with her; no one benefits from Rosa players having to carefully watch their inputs just to jab 3. In exchange for the uair nerf, a slightly better hitbox on nair (to protect herself) and about 1 frame less landing lag on fair (would generally make that move more applicable for the limited jobs it does for her) would help her worse match-ups while not really mattering to the characters she already beats.
Sonic:
Bthrow kills very slightly later (like maybe 10% later on average).
Very slightly decrease fsmash range, very slightly increase dsmash range (both are just a bit off, not big changes).
Play with usmash's knockback on early hits so it connects properly below 100% on Bowser and other bigs.
Otherwise no changes.
~Sonic honestly needs brought down just a peg, and the cleanest way to do this is to take his killing bthrow that rolls to ledges for you and make it kill just a bit worse. His fsmash has awkwardly much range and his dsmash has awkwardly little, and this can be stupid both in and against Sonic's favor and would be easily fixed. The usmash thing would be a buff for an already great move, but for serious, if you hit Bowser at 80% and he holds down he just gets out which is not good design.
Those are the only characters I feel substantially deserve nerfs, honestly only Diddy deserving nerfs that really hurt. A few I think warrant some sidegrading:
Zero Suit Samus:
Reduce kill power of Boost Kick by about 20%.
Boost Kick should connect the hits a bit more reliably.
Boost Kick no longer has RCO lag (this is stupid).
Utilt lag reduced from a million years to something reasonable.
~ZSS is really defined by how crazy powerful Boost Kick is which causes bad player experiences and makes her scale poorly to higher skill levels. Making it more reliable and not have that stupid RCO lag in exchange for making it kill later actually helps all parties, and to push her just a bit, making utilt's endlag less asinine would be nice.
Mii Brawler:
Helicopter Kick should have less base and more growth (so near edges it doesn't kill so crazy soon, should be about the same from other stage positions).
Fsmash's endlag could be slightly less comically bad (still should be unsafe, just not this hilariously unsafe).
Piston Punch glitch fix.
Larger hit area and greater movement control over Headache Maker (side-3); this move could be a useful tool to Brawler as a high priority move with just a little tweaking.
~Mii Brawler is mostly fine but has some non-trivial poor tuning on a few moves; this fixes them.
Villager:
Balloon Trip and Exploding Balloon Trip should have a ledge grab limit like Aether (can still grab by manually popping balloons).
Grabbable items should only be possible to stuff into the pocket once (so Villager can't repeatedly pocket the same item to permanently grief someone like R.O.B.)
Increase jab damage by 1%
Speed up all grabs slightly.
More landing lag on slingshots if not auto-canceled.
~Villager is probably the most polarizing character in the game. The first change removes any semblance of ledge stalling (not that it's broken or even good as it stands, just an obscure knowledge test to see if you know how to beat it) and makes long term run-away strats harder for him in general. The second removes a match-up specific abuse that shouldn't have ever existed. The last three things are about helping him in his bad MUs (making it easier for him to protect himself and approach defenses better than his) while hurting him in his worst match-ups (who just have no way at all through walls of slingshot bullets).
Then I think a lot of characters deserve buffs, but here are the notables I have thoughts about...
Zelda:
Jab should be less awful all around.
Back throw should kill about 20% earlier.
~Zelda is very hard to tweak without making her busted in FFAs, but seriously, she can get some help without doing that. A better jab would do so much for her 1v1 neutral without being a problem in other modes, and for how laggy her grabs are and the fact that she's a power character anyway, there's no reason she can't kill with throws.
Mii Swordfighter:
Gale Strike should retain damaging hitboxes for more distance.
Whatever up-1 is called should have larger hitboxes, practically combo the rising hit into the falling hit (so it could be used more like Dolphin Slash, not that big but still).
Airborne Assault could be less comically unsafe on block (still not safe but just less comical)
Aerial mobility in general needs to go up so he can practically space his aerials.
All aerials should have a few frames less landing lag.
Hitboxes on fair should be very slightly taller so he can combo the hits of fair together in more situations.
Fsmash should extend his arm a bit longer (for more range).
Usmash should kill somewhat earlier.
~This character is really awful, but this would be a decent start to fixing him I think.
Little Mac:
Full hop should go higher (able to FH onto SV's platform, able to double jump onto Duck Hunt's tree)
Uair should hit a far larger area, covering Little Mac's head, and should do double damage to a shield (I suggest a little whirlwind effect surrounding his fist to demonstrate the new, large hitbox).
~This is looking to fix the ability to lame out Little Mac without adjusting the various properties that could easily become dumb on the character.
King Dedede:
Almost every move should be a frame or two faster (for tilts it's endlag, for other moves it's start-up)
~This character is actually pretty close to functional, but his tilts being unconditionally unsafe and his other moves just being too slow to connect reliably in average situations is a problem. A modest speed buff for him is non-dangerous and could really help him a lot.
Falco:
Running speed improved somewhat.
Dair should start up about 4 frames faster.
Blaster (all versions really) should have a little less endlag.
~Falco could be really good if he actually moved when you ran, had a projectile that was somewhat better, and had a dair that was not for serious frame 16 which is not vaguely in line with the value of the move.
Samus:
Almost all hitboxes on normals need to be about 10% bigger.
Jab should actually combo.
~Samus would be... so much more playable with just this. She's so awkward now mostly because these things are not true.
Duck Hunt:
Jab combo should connect a bit more cleanly and reliably with the rapid portion of the jab.
~Duck Hunt's main problem is that he fails to protect himself, very polarized character except his problem is how badly he loses some match-ups. This would be actually a big help, maybe not enough by itself but would be playing it safe.
Mr. Game & Watch:
Almost all moves should do more damage, about half-way between the Brawl values and the Smash 4 values.
Turtle should have considerably less landing lag, close to Brawl safety (but less shield damage since it would do only half-way between Brawl damage and 4 damage).
Dsmash soutspot should have somewhat better kill potential (not up to Brawl level but better than it is now).
~G&W is really, really bad right now; the biggest problem is that his moves just don't hit nearly as hard as they should. His second problem is that he lacks approaches that have any kind of safety. These problems were not present in the honestly balanced (if often obnoxious) Brawl G&W so that's a good place to look (also the only version of G&W I'm aware of who was a functional character). This would probably be just a start but would put him back on people's radar as a relevant character.
Actually... I could go on all night and go through every character, but something along these lines would be very welcome. I'd also of course like to see Olimar's Order Tackle glitch and Palutena's Lightweight glitch fixed, Mega Man's utilt RCO lag fixed, for the new travel stages to no longer hit you while in motion (seriously this is obnoxious to literally all players not just tournament players and single-handedly ruins Mario Circuit), for Lylat to no longer pop fighters into the air, and for the clipping on stages in general to be improved so falling through them is more rare.
This kind of speculation is kinda fun and it's always interesting to take about what we would do with the power, but I hope everyone knows that whatever is in this patch is already decided (whatever it is) and that whatever we say here will never, under any circumstance, be read by anyone relevant from Nintendo. This is purely just for fun.
