Okay, big brain idea. What if we got something similar to Silver Surfer in the only passable F4 film Rise of the Silver Surfer? Something where they do mocap/CGI and then have someone dub the voice with some badass deep bassy voice? In that case I could see Danny DeVito and Morgan Freeman.
Wait, April Fools is over. Dammit, now I have to do a serious pick.
All jokes aside I think Morgan Freeman should do the voice somehow. For the mocap, they could find some experienced stunt double or, if worst comes to worst, CGI the shit out of everything.