I know that during Secret Wars II, The Beyonder put him back in his orignal body (which was destroyed in a fight with Terrax and Silver Surfer, cue him hopping into innocent guy nearby and bitch at Aunt May). if he has permanently switched bodies since then I do not know. Then again Doom does consider his own body to be the greatest I imagine. The royal blood running through his veins, and the fact that he was handsome or that every scar is a reason for him to remember or to go on. But like you say, cloning would be a great solution. unless of course, he considers cloning an abomination or something silly.