What a clever idea, I would make it if I could, but here's why I can't.
#1: I can't script, so I won't be able to make a script that allows you to put it on and take it off.
#2: I don't know how to make decals for Blockland, so I won't be able to make a decal for the shirt.
#3: Scripting is something you can't learn in 1 day, obviously.