Love the idea too, this certainly has my support
Don't quite agree with you on all your points Nomad, but I do agree that it probably won't have as much mod support as X9...mainly because of the fact that you have to have Vista/7 and a directx 10 gpu.
Now...if someone made a mod that unlocked FPSC X10 (so to speak) so that it didn't require Vista/7 and a directx 10 gpu to run (lower-end systems could simply not support certain features), FPSC X10 + mod might win over most of the X9 crowd, especially if the mod is free. Something like Airmod or the others that become like the backbone for other mods. This might be the jumpstart X10 needs to stay alive, should the migration lack some of the X10 features..
http://s140.photobucket.com/albums/r33/Sanky_Panky/Gabriel%20Acosta%20Unity%20FPS/?albumview=slideshow
My Unity FPS WIP