There's nothing 'wrong' with the 90mm f/6.8 - it's sharp and light and useful. The only shortcoming would be a small circle of coverage (so, a bit of rise or tilt and you'll start to get vignetting), and that even with a recessed board, on a monorail without bag bellows you might find those movements a bit stiff. You'll have to see. That said, it's a nice landscape and architectural starter lens, and when you get fed up with it's shortcomings (as you become more 'ace' at using it), you'll find a ready re-sale market with all those folks who are yet to buy a lens for their Wanderlust (Kickstarter) cameras (which are optimised for that specific lens).
When you do upgrade - if you still love 90mm, it's worth looking at the Calumet (poor Calumet) 90mm lenses - they are re-badged modern Rodenstock lenses and invariably cheaper because of that.
Marc!