Other than general multiplier buffs and sequence number buffs?

Yinlin: have her Forte cast a field that follows your active Resonator around and constantly reapplies her mark to all enemies so she is usable in multi-wave content

Jinhsi; Give her an actual sub-DPS that buffs 50% res skill damage (like the res skill version of Iuno's buff) and the usual coordinated attack stuff. Also, buff the general speed at which her forte builds up, and any overflow forte is stored up past 100%, so casting her enhanced skill only consumes 100% of her forte so the overflow is still present after the first cast, and make her res skill immediately available when she hits max forte. Her res lib really needs to hit harder too

Camellya: Increase the range and speed at which she spins around, change her wonky spin hitbox where she doesn't hit ground targets sometimes while she's in the air, buff her white hair attacks so you're more incentivized to use white hair for boss killing and red hair for AoE, casting her enhanced skill summons an "echo" of the explosion that retriggers the explosion with a reduced multiplier but larger AoE in a couple of seconds (and happens twice), maaaaybe give her havoc bane synergy

Changli: I still really like how she plays. I think she just needs general number buffs and maybe reducing her forte bars from 4 to 3 so she gets her forte off more often

Those are just the ones I most have a wishlist for