Simon,
Where I am (on Siargao Island), and my business that I am involved in developing, I am becoming out of touch with the UK airline scene and I'm not about to start speculating that NQY, indeed Devon and Cornwall, could become anything more than a "cottage industry" for aviation.
I believe there is a modest future for PLH if it were to re-open, those 30 years ago, initially, Brymon struggled for half fill a Twotter on the PLH/ORK route but when commercial started marketing that punters could travel by train to/from PLH to then fly PLH/ORK/PLH for less than it may cost from elsewhere, well all of a sudden Brymon were filling 50 seaters, never mind 20 seaters, on the ORK route.
Something NQY cannot offer is a thru rail connection but, as I was in discussion with certain people a couple of years or so back, there is a market for a "cottage industry" air operation in Devon & Cornwall, particularly if PLH were to re-open, perhaps operating a small fleet similar to Do228's/Do328's, obviously operating to an airport near to London, Manchester (for international connections also), across the Irish sea and to the Channel Islands, perhaps Brittany also.
A once a week Scotland (ABZ) 50 seater proved popular all those years ago so perhaps a modestly served Scottish route also but I can't foresee too much more than these.