Paul Walker usually plays one of those guys who comes off feeling like a stupid jock all the time and has never really matured past MAYBE high school. In my opinion lol.
First off, I laughed lol. Second, I kinda like the idea of Dicaprio doing it, especially if he could keep the weight off, as you've said. It would kinda be out of his usual choices I think, but hey. If he's expressed interest and is willing to do the work for the part, I would be more than happy to go into the next RE film to see Dicaprio as Leon.