Allowing more customization when making body mesh replacements would allow for so much more creativity when making things such as npcs and custom clothing. There’s a ton of things that could be made that currently can not be. For example, if you want to make the unturned character look like a cat or something, you are stuck with the basic walking animations and base hitbox. With more customization, you could make it look so much better.
Examples:
Animation replacement: allows you to link custom animations to the clothing and (if possible) have the hitbox follow the animation.
Hitbox replacement: having access to change the hitbox of npcs and players could lead to a lot more customizable npcs and player models.
Camera offset: Could work like the camera offset for vehicles. It’d allow for more vertical customization on servers.
Just allow them to work on Zombies: Self-explanatory
Not for body mesh replacements but still for clothing:
Allow_Equipment : Allows you to stop the player from equipping anything while they have the clothing on. It could work like the handcuffs but without the handcuff animation.
Cloud : Would allow you to make the clothing act like a cloud item. There could also be the same customization as on the actual cloud items.
Yes, I do know that there are risks to adding some of these but imo the rewards vastly outweigh them.