I personally think you can go on & on all day about markets, route to London, etc, but I feel it's all too complicated. It is in reality just a vicious circle if you have a large airport with many services & excellent access and passenger facilities then this will in itself attract more airlines & services & so it goes on, one feeds the other.
The economics of such a set up involve large volumes that facilitate the addition & improvements necessary to maintain & grow. This in turn makes airlines happy & attracts more pax. & more routes....
Until you can invest & grow such a model & reap the benefits of "volume" then you ain't going to get anywhere fast. In DTV's case then Peel clearly don't see this as a viable business model, when as it would appear they can simply access land and build whatever to support the local economic structure.
From a “non” aviation enthusiasts ( and there are many !) view, then this concept is itself not a bad thing. i.e. grow the local economy , increase it's wealth and the ability / affordability of it's residents to travel, with no specific agenda to seek out a local airport.
You can put any pax service into DTV, address the costs of doing so & hope the pax will turn up. But on a small scale operation doubtful they will in sufficient numbers as greater attractions elsewhere. History unfortunately counts for nothing, "we used to fly to London "x" times a day, so what ?
With efficient transport infra structure, once one has accepted that they have to travel to an airport at all, then the additional hour on road becomes less material & in that time c. 40 miles of travel create a much larger catchment area for the competition.
Unfortunately I can't see an answer on where to go next, the only way I see any way at all that DTV will ever "rise from the ashes" is not through the chasing of low volume low frequency UK destinations, is if they can place themselves in a position to attract and support a significantly sized lowco operator.
Unfortunately it is difficult to ascertain who is the more disinterested in pursuing and investing in such a project, Peel, or the Lowco's themselves...