I'd take a crack at Ironman but I don't much care for him now that he's the uber hero.
As far as the actual roster of the Avengers I say to go completely out of left field. For it to look like the Avengers, you just need two or three founders or their representatives on the team. Capt. Falcon and Thor already fill those spots, so let's see what happens. With the piss poor team rosters the All New All Different Marvel is throwing around we're bound to do better than 75% of their comics...
~KL~
Who says Sthor is going to be on the team :P We don't know yet, fun MYSTERY, EXCITEMENT.
Also you don't have to make Iron Man so uber :P