I wrote a function that changes your character's appearance to look like somebody else without needing to respawn. I looked into getting it to switch between R6 and R15 but that ended up being complicated, so it doesn't do that. Here's the code
https://pastebin.com/7j9fL7pf
and an uncopylocked demo place
https://www.roblox.com/games/929060671/avatar-change
say avatar/username or avatarid/userid to change your avatar.