Onion, your version of grinding to a halt and what constitutes a delay is based on DTV; I suspect most of the commercial operators do not find the operating restrictions onerous. I accept that a parallel taxyway will be a bonus, I was at NCL when they opened theirs and the difference in ground movement flow was substantial. The issue fior DTV is what would all the GA do if the airport increased their charges by the amount they would need to to fund such a development? The majority of movements are GA, therefore it would not be an unreasonable assumption to make that they would have to bear a proportion of the cost?
I doubt whether the council will prioritise funding for the airport ahead of essential services to their community at large.
The BIG advantage that DSA has, and why the risks of development were very different, is their catchment area. Not something DTV is blessed with unfortunately. Yes they had competition from HUY and LBA, not sure which other you are counting - EMA I assume. HUY has it's own problems, in many ways similar to DTV. LBA is a G*d awful place to get to if you live on the South side of LBA or in the Barnsley, Rotherham or Sheffield areas; and DSA is a better bet for this area than EMA.
I like DTV (although I hate the new pretentious name and Durham is equi-distance between DTV and NCL), I've worked there, flown from there and know people who still work there. I wish you well but please don't build your hopes up too high.