I hope what you say is true, although the problem could well be access. Cardiff airport is a long way from the affluent areas of its city.
Train access is rather swift from the main line station within the City (Close to Cardiff bay) into London.
I would wager that the train will be more expensive, well it needs to be if folk are to travel from Barry to the docks!
I remember well, the business plan for Fly-Europen (BAC1-11's) from Barry to London Whipsnade. It never happened.
Good luck AW, for when the baby WDA funds run out, you could be on your own?