Clueless;904794 said:
I'm thinking of removing the whole assembly and weld in a piece of metal to over the hole where the sunroof sits.
Any competant bodyman should be able to do this. It will work best if you can get a roof panel from a wrecker so that the curve matches the factory profile. Also look for a headliner, since this is also going to have been destroyed.
You might also want to consider replacing a larger area, since there will have been screws and other hardware pushed through the roof, and it may have been deformed in order to make the sunroof fit.
I'm surprised about a lack of headroom, though. I have plenty of clearance over my head, and I'm not particularly short. I also have the power seat completely lowered, though. (I presume you've adjusted this?)