Don't ask me why (as I usually can't stand the guy
) but I think James Spader would look good opposite RDJ's Tony Stark, not necessarilly as either TM or CD but as one of IM's rogues gallery certainly. I guess it's because he can play such a convincing a$$hole that I figure he'd make a good villain.
Failing that; Verne Troyer can play Titanium Man II (a.k.a. the Gremlin)
Now I'm gonna lie down and try and work out were this sudden and disturbing liking of Spader has come from..............