I agree that Wendy herself doesn't need much of a change, but if every character is getting a rework then I wouldn't mind too much if she got one or two small buffs to make her solo play (i.e. while Abigail is on cooldown) a little more unique.
The real potential with her rework would be the interesting abilities that could come with buffing Abigail.
Having her work together (no pun intended) with Wendy could be really useful. For example -
A small but obvious change to Abigail's AI so that she doesn't die so needlessly.
Call Abigail to temporarily possess Wendy, causing her to hover and increase her movement speed, allowing Wendy to cross small rivers like Wortox and the WereGoose can
Command Abigail to possess enemies (perhaps 3 or 5 at most) using a haunting AoE aura that causes the grouped enemies to become followers that will work/attack anything Wendy interacts with. The length of the posession could be tied to how much health the creature had at the start of the possession, for example, Spiders/Frogs/Bees would stay possessed for a whole day, Pigs or Werepigs 3/4 of a day, Beefalo/Tallbirds half a day. Monsters or Seasonal Bosses with large amounts of health would be pacified rather than being possessed.
Reanimate the Dead! Possessing bones, bone shards, hounds teeth, player skeletons or lost survivor skeletons would increase Abigail's defence or attack damage depending on the reanimated object. Bones for defence, teeth for attack damage, skeletons for defence + attack damage (you could even see the makeshift skeleton body jiggling within Abigail)
Item Levitation. Allow Abigail to defy gravity by levitating that heavy item at normal walking speed. Don't have enough Inventory space for that 1 important item? Want to relocate a structure that you placed incorrectly? Let Abigial carry it for a change!
Any changes would obviously come with their appropriate Sanity/Hunger/Health loss, but I would be really interested in seeing Klei come up with some Abigial specific abilities for Wendy's rework.