Durbs. I hope you use magic lantern on the 7d
Also stitching the photos would take an age by hand (although I presume there would be a software solution??).
If you are going to do this seriously, may be worth investing in a newer DSLR? Most new ones have a built in interval function. You can get external power supplies too.
Don't know sorry, I assumed they would. My Pentax K7 is at least 6 years old and has it.
2) The build will involve welding, which produces very bright albeit localised light. Anybody got any idea how big an issue this is going to present? I've seen time lapses in car manufacture with welding and it seems to work ok, but are they doing something tricksey for the frames featuring welding? I guess some welding in the test lapses is the way to go...