I've used SLIGHTLY puffy batteries before and yes they do work, but it always scared me, always worrying about my plane exploding. On top of that i noticed it doesn't have as much power, so in my mind at least that would make me think you have to run the battery harder which just makes the condition work. What i would do is keep it but not use it on any plane you value or has good parts, wait until you get servos that have taken a beating and a motor on its last breath. then slap together a little fun project and do something stupid with it, just please don't try and make the local news.
By project you mean exploding it for scientific reasons
Everyone loves to see someone stab a lipo with a screwdriver and see it explode on youtube.....