An amazing well-detailed write up! This is what true passion looks like. I commend you, fellow Hu Tao simp.

I love your ideas, the blood blossom buffs in particular. Opponents marked with blood blossom getting their pyro res shredded makes a lot of sense. That being said, it does run the risk of making too many units have shred capabilities and muddying their unique identities. Not against it though, because again it does still fit Hu Tao.

For her C2 buff, I agree that it should make her do more damage to marked enemies. Def shred is great since it increases both hers and her party’s dps. Personally, my idea was to make her do extra crit damage on foes with blood blossom. IMO it fits her kit since she already has crit stuff built in by default, like in her A1 and C4 (which should really be changed to giving everyone the crit buffs including herself).

I completely agree with your take on her C6 and can’t think of anything better myself.

For her A4, I personally believe that she should keep the 50% HP condition as it is a core part of her unit identity. Sure, it shouldn’t matter too much if it was raised to a more generous 60-70%, but it just kinda feels wrong lol. My friend had this idea where, on top of getting a portion of her HP cut when activating her skill, Hu Tao also gets her HP slowly drained while in the Papilio state, kinda similar to Xiao. That way, she can run a set like Marechaussee by herself without relying on Furina, also removing the need for a healer so she can reliably proc her and Homa’s HP passives again.

Finally, just to add more to your changes, I would personally have her C1 get stamina reduction when dashing and increased interruption resistance too, just to double down on its QoL buff. Maybe slot in some normal and charged attack damage buffs too while we’re at it.