How would you change Pit's moveset?
Use a mixture of Project M and Brawl Minus alterations.
Up Special: Brawl Minus (think Villager's Up Special). I will 100% swing to the PM side if you give him 2-3 up special uses to replace Brawl Minus's freedom, and make the shield invincible, like it should have been.
Side Special: Project M (glide). Buffs his recovery even more. His mobility on stage has also been increased. Where side special is a kill move, it's completely predictable. With side special, not only can Pit be in an opponent's face lickety split, but they won't know what's about to hit them. Replace the glide attack animation with an homage to the tr4sh side b. He doesn't go into free fall after using it.
Neutral Special: Project M and Brawl Minus both do a good job here. B- gives more control but PM gives more speed. You can't "snipe" dudes with B- but you could pull off more shenanigans.
Down Special: I can't remember if there's any difference. Just use Brawl's shield style and not tr4sh's, but let Pit turn around with it. Let him jump cancel it too, and take away as much stun from reflecting as possible. I would be willing to let go of its ability to block physical attacks and to turn opponents around (like caping Ganondorf's Wizard Foot).
Taunts: I can't remember what they are in tr4sh but if it isn't Brawl's then fix that.
As far as tilts and smash attacks and aerials go, I don't know enough about Pit to put forward a well thought out opinion there. Still, I've got things to say. I like PM's dair. It is a floaty killer which I think should be the focus of Pit's character pragmatically. I also like the spike hitbox but it's ridiculously short and small, so I'd widen the window for that. Fsmash is a must. I like his multi-hit up smash; though, it's too laggy and dramatic in tr4sh. Down tilt is great (it's like Peach's)---it can combo on stage and kill off stage. Ftilt is decent, as it gives him much needed range. And nair's pretty good.
As far as costumes, I liked Brawl's green (which is in tr4sh), blue, and gold. He has some great palettes.
But yeah, I think Pit's niche is mobile sword character, which he shares with Meta Knight. The difference between them is that you sacrifice kill power for more defensive options---the shield and the arrow (in terms of zoning; but obviously, it's good as a projectile in general, which MK lacks). I personally prefer Pit over Meta Knight, so it would be a shame if Pit was made more similar to him than he already is. And like I said, he should be thought of as a legitimate floaty character counter. He should be able to confound them with his speed and range, and kill them with his vertically launching moves like PM up-special and dair.
Ask this guy if his tunes can be put in the game.
Especially
this. ("Sky World")