It would be funny if they got Ninja Theory to do it. Seriously though, some better writers would be really cool. This criticism applies to most Capcom games. Atmosphere is also really important, and they didn't give it enough attention after 4. I would prefer if they dropped the co-op as well. The feeling of isolation was something I enjoyed before they introduced that, at least with Ashley you didn't have her around 100% of the time. Plus when she died it sucked, but it at least sucked because it was your fault, if your co op buddy dies you just get mad at them, and if your AI partner dies it just feels like you're being punished for not getting a real person to play with you. As far as the puzzles and stuff go, I'm not really sure, all I know is RE5 did a bad job of breaking up the shooting segments.
In case anyone is having trouble with the t-rex butts in (or just outside of?) Izalith, I just thought I'd mention that many of their attacks will damage other guys nearby. And since they don't respawn, you can clear them out a few at time by drawing them out with arrows then running into the middle of the bunch. In my first playthrough, I think more of those guys died to each other than to me.