Nice idea! For shots where you need to show the 2003 Hulk, despite being long shots, maybe you could just make him a bit darker to blend better with the 2008 version.

You know, it might sound weird, but overall, I was more impressed by how Hulk looked in the '03 version, especially given how much older it is and how much better they could've done with the '08 one. :p At least the '08 one was more consistently-sized.

Have you seen Jorge's edit of the 2003 version, chickenfish? I love it! http://fanedit.org/280/