i think this would be a good idea, like maybe have him only able to use melee with kaio-ken, or perhaps use it in a PS to boost PL, but this would drain his ki VERY VERY fast. These are excellent ideas IMHO as this is all he really uses kaio-ken in the series forAlso when Goku goes Kaio-Ken couldn't you limit the attacks and abilities he can use? This would solve his too strong issue.