Just to let you know, the Witcher 2 was designed straight on the PC. It was one of the only games still designed for the PC by PC people. While the idea of putting it onto the 360 was there at the beginning they still dedicated to making it the best on the PC. As for remapping the keys, I honestly never check on most games but yes that would suck if you couldn't remap them the way you want.
I think CDProjekt always had a controller in mind for it (and eventually the console). When I first tried to play it, I couldn't remap, but it was hardwired to switch it over to an XBox controller with no problem. There are still keys hardwired in spite of the remapping making it awkward at times -- with the spacebar remapped, I still have to use the spacebar in a few places as it ignores the remapping. ME2 was the same - IMO both were designed for a controller and the PC version lost a bit because of it. Particularly the tactical camera. Easy to get hung up in a corner somewhere with both games - sometimes funny, sometime just annoying.
So while both BioWare and CDProjekt claim it was designed with individual platforms, I don't fully believe it. I probably will purchase ME3 for the PC, but it will be well after the release date.