Well, the cool thing is that aside from the JDM sidemarkers, no metal was actually cut in the process. The patch pieces were made from a scrap NSX quarter panel then bonded (read: no welding) in much like the inner fender reinforcement is. Remove the filler, prime the area then spot it in, and it's close to OEM again. There'll be no issues with corrosion or anything as none of the inside was touched and the outside (obviously) is painted.
Regarding the roof - the berlina can always be refinished. I've got the OEM mirrors, the OEM interior pieces, the OEM wheels/hood/wing/carpet/etc - any part I need to revert it "closer" to stock if desired.
Truth be told, I don't plan on getting rid of the car anytime soon. The only reason I even got this was because my old one was wrecked. If and when it is sold, there's a good chance it'll get sold as it sits, with the OEM pieces separate, to someone looking for something like this. It's killing you to see it like this, but it's exciting to me - it's exactly what I've wanted to do since I first started seriously looking at getting an NSX 3.5 years ago!
Ryan