Why doesn't the Immortal just cosplay as a viltrumite?

If he shaved his beard, grew a moustache, and changed his suit, he could cosplay as a viltrumite, and though this would serve no purpose, it would make him feel better about himself for being weak, and maybe he could even try and fit in with real viltrumites for a bit, it could even be fun for a while, and since viltrumites don't fight viltrumites, he's mainly be fighting non viltrumites most of whom he'd be able to easily overpower, just like a viltrumite. maybe if the viltrumites figured out that he wasn't nolans Much older son (that would be his cover story, he is marks older half brother) they'd pretend out of pity for him and his weakness. Viltrumortal for the win.