I'm going to start researching/working on this immediately. Let's make this a community effort!
With our combined knowledge and skill, we could really hand Crytek their asses by releasing a homebrew Crysis 2, with Crysis 1 graphics.
EDIT:
Just so everyone understands - which a lot of you don't. Since at this point in time it's next to impossible to mod Crysis 2 to take advantage of CryEngine 3 effects (if it really does support DX10 and DX11 which I am STILL suspicious that it doesn't), the idea is to import ONLY THE MAPS into the CryEngine 2 editor so DX10 effects can be added along with other graphics mods like Lifesis or CCC which are currently impossible to implement in Crysis 2.
The game will end up looking just as good as the original Crysis once some texture work is done, and will run just like the original Crysis because the CryEngine 2 will be doing all the work - It's just reading the maps. It might even run smoother than the original Crysis due to the small cramped maps. We will be using CryEngine 2's DX10 lighting, shadows, volumetric effects, particle effects, high res textures, etc.
It will look A LOT better than what Crysis 2 looks like now with CryEngine 3's DX9 effects.