I don't think there has been a thread on this yet but I have noticed that Blackpool Airport it to reopen to scheduled fligts again on the 1st of April with new owners.
From a personal point of view I feel yes the airport is good for business in Blackpool but I can't see it being ever viable. With a half hourly service to Manchester Airport and hourly to Liverpool South Parkway for Liverpool John Lennon Airport I can't see the demand for flights in Blackpool ever taking off.
I feel that Blackpool Airport will again join the long list of Kent, Sheffield City, Swansea, Plymouth City, Coventry and Shoreham of small regional airports that tried to be big in that 1995-2007 period that failed and are now closed or just used by private aircraft.
What does everyone else think?
I can't see Blackpool doing well just for the pure reason it is close to Liverpool and Manchester Airports. Which is the same reason for most of the other ones you mentioned.
Shoreham is too small and doesn't really have an area to serve (Portsmouth is served by Southampton Airport) Brighton itself is served by Gatwick. And you have Lydd Airport which is almost in the same category but could have potential (In the fact it is close to Ashford, Folkestone and Dover)
Kent, did have a lot going for it in the fact it had a long runway and was close to the railway, but wasn't really in the best of places to serve many people (Other than Margate and Ramsgate)
Plymouth, had the problem of being too small and another short runway. But if you were starting from scratch Plymouth would be a much better place for an airport than Exeter and Newquay. As it is in the centre of Devon/Cornwall. Newquay is a bit too far away from most people (But is big) and Exeter is a bit too close to Bristol. If say the runway at Plymouth was almost double the size then I think it would be very busy to the extent I think Exeter and Newquay might well have closed.
Coventry is an awkward one, yes it is close to Birmingham but a lot of major cities can handle two airports. (e.g Manchester/Liverpool) So I think we could well see passenger flights from Coventry again sooner or later. Wouldn't surprise me if Ryanair decided to start up a base there.
Sheffield was too small as well plus the Peel Airports were opening and investing in Robin Hood Airport nearby and being in close proximity to (East Midlands/Humberside/Leeds and Manchester)
Swansea is the same as well, too small, too close to Cardiff (Which was also struggling. Maybe one or two flights from Haverfordwest might work, to Dublin and Amsterdam (As it is further away, but the market is too small)
Tees Valley airport is another odd one as it is in a good location near Middlesbrough (Which I personally think would be a better name for the airport) it has a decent sized runway and is close to the railway. It would be a real shame if it were to close. In my eyes it could be easy to do, firstly build a new railway station which is fit for purpose, secondly I would rename it Middlesbrough International Airport (Just as I think that would attract more business). And the third thing being a long shot, slightly reroute the proposed London - Middlesbrough train via the Airport. And the most important thing is to convince an airline to set up base there, either a tour operator and or a low cost airline, and maybe even a flight to Heathrow)