Being on the tripod and needing most of the real estate work to be in focus, stopping down to f/8 and using iso 100 or slightly more shouldn't be to big of an issue I'm thinking, for that type of work...I do use my tripod always for Real estate images and my flash as needed. I know the FF sensor won't solve all the issues with that, but it accepts so much more light than my crop sensor on my 7D, I thought it could be very helpful in post... My 7d has major challenges with noise in the shadows...
Depends -- if you're shooting at f/2.8 to get faster shutter speed, FF won't really help because you need to stop down to get the same depth of field so it's a wash. Shooting at f/2.8 on FF is like shooting at f/1.8 on APS-C.
So bottom line is -- FF will help if you're shooting at ISO 100 and f/8 but not if you're using it to get higher shutter speed. Also, fast lenses won't necessarily help much, distortion characteristics are more important
regarding tilt shift the two things it buys you are optical correction of perspective distortion (e.g. straightening out converging verticals for example which is a common problem with wide angle lenses) and also they can help add depth of field
The tilt shifts sound intriguing, I imagine expensive too. Seems like the majority feels like a wider zoom like the 24-105mm isn't a good idea. If I'm going zoom I need to look at the 24-90MM, I'm thinking version 1 or version 2 would be fine.
Seems like primes are the most recommended lenses though. I'll start pricing out 14mm, 24mm, 35mm and probably look at a 50mm 1.4, although it sounds like that might not get much use... maybe not wide enough...
Thanks for all the help guys!