I've managed to use SC for this since you have the ability to kill someone and take their appearance but if I keep using SC it will affect everyone on the server since it's done via serverscript and tryting to do it with localscript didn't work out so well
Use HumanoidDescription
Though I'm not familiar with it myself, I know you can set existing roblox asset ids to its properties and apply shirts, pants etc. Custom meshes are not support, however. It's extremely customisable in terms of as if you were editing your own character. I suggest you read an article about it to get started!
Extra note: this instance goes into the player character, meaning you can set different characters for each player!