Sounds like a TS-E is the way to go, what body are you using? You want to be full frame, if it's stills only then a used 5D classic would be a good starting point, if you aren't FF already.
There are a few hire places around, why not hire to try before you buy?
That way you can get used to the idiosycricities of TS-E lenses (over-shifting can bring in fringing and vignetting, fall off) before deciding to commit to a hefty purchase if it isn't going to be for you.
If you hire from Calumet I think they have a policy of refunding the hire against the purchase cost of the lens, worth looking into at least.