While the club gives me carte blanche on design and a modest budget, I'd have my guys clearing the gorse from behind old #7 green also clear 50-100 yards behind #7 tee and cut a new switchback from #6 green to a new back tee as high and close to the road as possible. # 7 would now be a par 5 running in the opposite direction of the only two other 5s (9, 12). I'd wait to see how it plays before adding fairway bunkers and or scruffy areas, primarily on the right.
As to #8, I'd clear most of the gorse behind old 7 green all the way down to the bottom of the swale. I'd locate the primary tee where the green currently sits, maybe push it over a bit to the right near the gorse to enhance the dogleg. I would put another tee behind that one tight against the gorse, maybe 50 yards or so, carefully considering the barrier between the new 7th green and the new back tee for #8 (which would be open primarily for serious competitions).
As to playing 8 down 9, it may be done by accident, but I doubt that most Dornoch golfers would attempt that more difficult route. If it becomes a problem, clear more fairway space before the drop or put in the dreaded in-course OB.