I can't recall what the rear is like in the Strad (anyone got a picture?) Is it really that different underneath whatever trim panels are in there? I'd be surprised if the metal work underneath wasn't the same? You wouldn't need seats, just the Isofix anchor points, and they're bolted to the bodywork, not the seat.
In fact, I've removed the base of my rear seat to prevent it getting dented and damaged from the baby seat and it fits lovely! (also no spillages on the seat)
The insurance implications of making a two seater, three, is a different matter though.