Coventry - viable long term?
If they have a fraction of the freight traffic they once had, a couple of business aircraft a day and a scattering of general aviation flights, that cannot pay for the costs of running an airport of that scale - by miles. You'd need another ten plus 'proper' commercial flights day to get back on your feet again or a huge increase in overnight freight traffic. Birmingham is busness aviation-friendly with reasonable costs and a choice of handlers whilst parking fees are relatively cheap.
It's going to be a very tough gig to get back their feet. Any new investor needs to come in with property development angle and that rests wholly with the councils being willing to give a free hand to that buyer to do something radical. The property side will have to underwrite the cost of keeping the airport bit going, but if you can't build anymore stuff to rent out, the money's not there to keep the airport going as an airport.
What you need is a racecourse, film studios, football stadium, expo centre, F1 track, golf centre, health and fitness centre, offices - you name it, anything that can fit in on that footprint whilst still keeping the runway going.
Good luck, we don't want to loose you, but the whole future rests with planning authority's willingness to give a free hand to the next leaseholder.