I've come up with a short list of improvements for Peach.

-She should have a both a running throw (larger range) and regular throw (average range) for her turnips. Running throw really helps with edgeguarding and ground game. Also, turnips should not hit opponents towards you, it should hit them away. I've hit people offstage with turnips and it has HELPED some opponents recover, that's a little ridiculous.
-D-smash should have more knockback on the first hit, i.e. if someone DI's out of D-smash it should send them further away.
-Her Dash Attack should be the Melee dash attack imo. This means that, when its thrown out, Peach quickly moves in the direction that the attack is used in. The hitbox should send opponents up (like Melee) for the sweetspot for aerial setups or to grabs on fast fallers or large characters. The sourspot weakly pushes them away.
-F-air's hitbox should not have as big of a vertical knockback hitbox because it makes it extremely hard to KO opponents. The majority of the hitbox should have decent sized horizontal knockback while the very top (and first) hitbox should hit upward, thus giving the user a reward for landing the good part of the move rather than the top.
-I would also like her dash speed to be just a little faster for situational ground tech chases, but this isn't that necessary.