noshi

Yep. The idea in consoles is already there with double analog sticks but trying to access the right one for aiming is not ergonomic. One game I played where the mouse has limited movement (before having 'negative acceleration') is the Prince of Persia series on PC. The camera can move only as fast as the analog stick can, which is about 400 DPI or so, even with mouse input. It's also hard to move without an analog stick because a lot of movements in that game are not cardinal directions, and that screws up jumps with awkward camera angles.
If anyone wants to know how will it feel like using an emulator for mouse/keyboard on xbox 360 it will feel like PoP or N64 emulators. Slow and sluggish.