Jiggs needs less landing lag and ending lag on aerials (except nair and fair), more power on fair, and better linking dair. Then less endlag on tilts and smashes and more horizontal throw angles (not comboing is fine). This admittedly makes her more similar to Kirby, but they'll still be quite different.
I think jigg's gameplan goes from ground->air->ground->air a lot and it'd be nice to have better tools for that. There is no saving her bad specials. Pound and rest are workable enough.
Or we could go with the other idea and reduce landing data for all characters. Melee's was good, but it made sense since everyone fell much faster while Brawl's was a bit too good? Eh, I don't know. Smash 4's divided between really bad like Bowser, Charizard, Triple D, and Shulk who some may have good auto-cancel windows, but generally have high landing lag and really good like Captain Falcon, Cloud, Fox, Ryu, Sheik, and ZSS who have either really good auto-cancel windows and/or low landing lag on moves that really matter like Captain Falcon and ZSS's Uair have only 9 frames of landing lag while other flip Uair users have around 12 and above. In some cases, auto-cancel windows don't even matter like Fox's Bair's landing lag of 15 frames is probably never going to happen, so why not just lower it to 4 frames, the hard landing from auto-canceled aerials, then? I mean, the auto-cancel windows on it suggests it's not even meant to suffer landing lag. Some moves have really stupid landing lag like Falco's Fair used to have 32 frames - now it's 25 -, Fox's Fair has 27, and Sonic's Fair has 26. None of these moves are powerful, spammable, or so damn good they need high landing lag like that. Yes, Fox and Sonic run really fast, but guess what? Their Fairs if spammed, will become pathetically weak and they're already pathetically weak damage-wise; Fox's only does 7.4% and Sonic's only does 7% assuming they fully connect. Meanwhile, Pikachu's Fair which has 15 frames of landing lag and does 9.8% total. Both Pikachu and Sonic's Fair auto-cancels from a hop, but who's getting more reward and whose Fair is safer?
Moves that have really good landing data becomes really noticeable like Cloud, Ryu, Sheik, and ZSS's. Sometimes, it makes sense since Ryu's aerials outside of Bair and sort of Fair have short range, but for faster moving characters that also have good range like Sheik? Okay... What about Marth and Roy? Or what about Falco, Fox, and Wii Fit Trainer? This along with the 30 frames of landing lag on recovery moves should go down. There should be outliers, especially if those are really strong moves that can be high risk or low risk like perhaps Luigi's Super Jump Punch shouldn't have 20 frames of landing lag, but say, 40-ish instead of 68 since it's seems to be the gamble-type move where you either succeed or fail horribly, but (Dr.) Mario's Super Jump Punch? Yeah, it shouldn't have 30 when ZSS's has 23.
I've felt for a while that ZSS' Uptilt is a "broken in theory, but not so much in practice" move. At frame 3, it's as fast as, or faster than, most characters' Jabs. Heck, most characters'
anything. It also hits on both sides immediately, something which is very rare for an Uptilt, and extremely good for a move that has such an obvious "anti-air" design. It also has amazing invincibility. It also can kill. It also does 12% if both hits connect, which is crazy high for a tilt, especially such a fast tilt on such a fast character. In fact, it might have the highest speed:damage ratio for any tilts?
In practice, you don't see ZSS players use it much. Partly because it's difficult to find a use for it, since the most I see it is out of a perfect shield as a counterattack, and ZSS has other options there, such as UpB, Jab, and maybe Grab. Partly because the rest of her moveset is at least as amazing, so it's not as necessary to use it
Don't forget that it's recoilless and, I think, transcendent!
ZSS's Utilt is good, but she just has more moves to use and can do similar things. It's kind of like how Lucas and Ness have really good Dtilts, but they've got other things to use and it might not be the move for their game plan. Now, if Fox or Mario had Lucas or Ness's Dtilt, but with their own Dtilt's range? They would go ham with their even better close combat game. Actually, wouldn't that mean they would have a Dtilt confirm to their kill moves? Fox with Lucas Dtilt to Up Smash or Mario with Ness Dtilt to Side Smash. Sometimes, they're just rare moves you don't see being used, but are integral to a characters game plan like how Cloud and Mega Man's Dtilts let them slide under projectiles and act as a burst movement, but they're generally doing other stuff like Cloud would be moving around and playing with his Nair while Mega Man is moving about pelting you with lemons. Now, if say, Luigi, a more grounded fighter had their Dtilt? Welp, you just solved an issue about Luigi's need to perfect shield projectiles to not slide back against them and you gave him an incredible burst movement option. In some other cases, a character would just prefer having someone's move like Falco's Utilt is great for anti-airing, but its hitbox is central to his body. ZSS's anti-airs too, but it has more horizontal range, more safety when it's recoilless, and transcendent while also lowering her hitbox. Falco would love to have her Utilt because of all that plus it would look stylish. Seriously, I bet even Wario players would want to see Wario do a move like that.