Just had a thought... over 100 years ago Henry Ford set a LSR on a frozen lake (Lake St Clair)
Given the difficulties in getting enough length at Bonneville etc, has anybody considered a frozen lake?
It's level, it's smooth and you could find one far away from anybody who might complain. OK, traction is a potential problem, but you could roll in some hot gravel and sand which would provide the grip. Then come the spring when the ice melted, the surface would just sink to the bottom and being inert it would have neutral environmental effect so the tree huggers couldn't complain.
So, what are the snags?