Those creatu you mentioned (with the exception of the narwi) are older creatu and when they were created, the artists weren't as experienced and Res had people who did not know anything about concept design. As since these are the 'original' creatu, people will hate the artists if they ever changed their designs completely. If you look at more modern character design (not on Res, but in like games and fantasy stuff) you see less 'this plus this' and I can also see that Res is aiming to have designs like that. If we go back to just adding two animals together, Res will not only go backwards on themselves, but also go backwards in the whole design industry. I would never wish to see anything so dated on this website because I know that Res is better than that.
However, I look forward to seeing your new ideas. Don't take my comments to much to heart; I'm just a bit synnical now.