So from the perspective of someone that fights against link quite a bit more than actually playing him, I've come up with some stuff that I think he needs (well mostly I just agree with stuff already posted).
Fixing uair hit bubble - I thought I fixed this ages ago in like 2.6 or something, but it seems it was overlooked for a very long time. There is absolutely no reason why this should still be a thing, especially considering that all the other hitbox fixes were implemented. I've heard interpolation as a counter argument to this fix, to which I say, move your cursor from link to the right one character space, pick that character, then use uair, and notice it's the same exact move with full coverage of his sword, then try to still have that argument against it.
Faster jab - Not much to say here, it comes out on frame 6, but that part is never going to hit anyone. So really it's a frame 7 jab, which is pretty not great, frame 5 would be a reasonable fast move for him.
Faster utilt - Same as jab only not as important or as obvious, keep the damage and endlag nerf, they're pretty fair. Making it faster gives an incentive to use it over usmash.
Ftilt being useful - It's unanimous, ftilt is a terrible move, and it does absolutely nothing useful except giving you another reason to pick a better character. Making it hit at lower angle is the most sensible fix, as he has no moves that hit at low angles, except the lasting hitbox on spin attack, but be honest, you're not hitting a good player with that usually. Though I imagine they'll just add some extra kb to it and call it a day.
Nair increase in damage - It's a little underwhelming atm, I wouldn't put it in wet noodle status, but it's close. I could see a 1% increase, maybe 2%, but a 12% damage nair is the standard I believe. With 12% nair he'd actually kill things off stage instead of pretending he could.
Now that's all the stuff that most everyone agrees on, so let's begin on some stuff that might be questionable.
Added percent on up b - Debatable on how much, but giving link another chance to bomb jump or being able to use it offensively once without sacrificing his bomb jump, is pretty big imo. Currently its pretty easy to steam roll through his recovery, but with an extra bomb jump, he'll have more than one shot at cheesing his way to recovering. His recovery options should still be fairly easy to hit him out of, otherwise his recovery would be back in 3.02 status.
Usmash nerf buff - Now this is something that will probably cause some disagreements, but usmash currently, imo, is better than utilt in pretty much every regard that means something, and the only way to differentiate the two is to make usmash a kill move, instead of a combo forever move. With the added kill power though, it'd have to have a little more endlag to balance it out and give more weight to the move. The extent of which, I wouldn't be sure of, but it wouldn't be too extreme, 2 or 3 less IASA most likely. The amount of kill power is something that's debatable as well, testing would have to be done to get a reasonable value.
Bomb adjustments - (limited knowledge on bombs so keep that in mind) I've heard from mostly empty sky on here that bomb distance sucks, and Beorn tells me all the time that he likes them, so it makes me want to ask, why not both? Since the distance is shorter in this version, you could have the shorter distance on a regular toss, and then have the previous longer distance toss when you smash the control stick. I'm usually not one to advocate having the best of two in one move *cough cough mario fair cough*, but pulling a bomb has hella commitment, adding more versatility to it's throw distance doesn't sound game breaking
And now the thing that no one except maybe Beorn will agree on.
Boomerang nerf buff - Now before you jump on my case about boomerang being not over centralizing and link needing it, ask yourself this, what's been the one constant issue for balance concerning him in almost every update? Whats the reason people think he's so good? Why do people hate him?....the answer is always boomerang. It's been done over and over, and the results have shown that every time the speed he throws it increases, the cool down decreases, or the angle changes (sometimes all the above) he instantly breaks into a dumb character. Link has too many projectiles and options to cover space for boomerang to work the way it does, that's why so many people hate him and call him bullet hell the character. Notice also how toonlink's boomerang comes out on frame 27 and it's just fine, lol 19% though. So nerfing the speed it comes out and buffing the % it does would make it's usage more thought provoking, net a fat % while limiting their options, and covering your poorish movement, sounds like a win win to me.
I'd post rando buff or something I thought of at the end, but I've spent enough time on this already. I could've made it shorter by just saying I agree with beorn, but there are a couple of differences here and there, so might as well type it all out. I really hope the pmdv takes a look at some of this and takes at least half of this into consideration. If not, I'd be extremely disappointed in how they're handling this character, but that's kinda been the same song and dance it's been for most of this game's development, so I guess that wouldn't be anything new. Sorry for the huge wall of text btw, I've been kinda inactive lately and had to make up for it. Feel free to agree or disagree, I'm not a link main or anything, but I like the character.