LHR-NQY
Would love to see LHR-NQY, would be on it frequently now that the fun's gone out of driving (price of petrol, congestion, speed traps, etc.) which is tragic bearing in mind the improvements on the A30/A303 over the years!
It's also the best London airport for NQY because of connectivity with longhaul flights, which helps with make "thin" routes viable.
However,
(1) it won't happen unless and until LHR is expanded, making slots easily available and the slot market is ended;
(2) there would have to be some arrangements for lower airport charges;
(3) domestic APD would need to scrapped or go back to Ken Clarke levels (he introduced APD in the 90s);
(4) as a "thin" route, LHR-NQY (and similar) would need smaller aircraft of the type that BA don't have and some frequency, so would not expect BA on the route, that said, interlining arrangements/code sharing with BA/VS could be possible;
If LHR does expand and gets a new longhaul routes, additional "thinner" domestic/near abroad routes will be required to feed these, supplying the connecting pax.