Like PF I am from the old school, I have been filling charters ex CWL since the 70's and was one of the two founders of Air Wales in 1999 ( its first flight was much later after RGDT backed the idea) and I believe the following.
No LoCo is going to be interested in setting up a base at CWL or NQY simply because the traffic is not there, what the airport charges is important but not vital. This does not mean new routes may not appear but equally some will disappear. If the terminal is a shed it doesn't matter to the airline as long as the route is profitable.
The business is very cyclical though and all that may change in the fullness of time, perhaps for the better and perhaps like PLH for the worse.
There is still though business for a small Do228 type operation and had AW stuck to that they may still be around, low cost to the airline not the passenger. I would rather have 3 passengers paying £300, than 15 paying £50!
To help rebuild CWL, NQY etc now needs innovation not dreams of big jets, it can be done, it need not cost a fortune and is possible. These are marginal airports and need smaller planes to serve it.
Finally please stop comparing CWL to BRS, it isn't BRS, it is a different catchment area, I have driven from Cornwall and Devon to catch a flight from BRS but if the second choice was CWL I would probably rather drive to LGW or LHR instead.
That is my thought anyway but in my dreams I would still like to see a major new airport next to the M5 and the railway at about Wellington in Somerset with easy access to the entire area and routes Worldwide.... dream on!