The most recent 'Welsh' airline closed down because it over expanded itself going from Do228's to ATR42's, Wales wasn't even able to sustain a local scheduled service ATR42 operator and now some dreamer(s) imagine a 'Welsh' airline operating regular transatlantic's that no other UK operator has been bold enough to consider viable, but then they envisage operating to European cities also so now they're planning a mixed fleet of a long haul jet or few and some short range turboprops or pocket rockets.
Air Wales couldn't even make an ATR42 operation work but had they stuck with Do228's they might still be going now and what it might take is for another Do228 operator to take the place of Air Wales, to learn from their mistakes.
It has already been mentioned that 'Welsh' airlines have expanded their businesses outside of Wales, of course they have, with Wales only having one commercially viable airport what else should be expected?
Another airline to try close European city schedules from/to CWL was Manx Regional with Jetstreams back in the 90's, they failed miserably, I actually took a day trip to BRU with them one day, a few passengers on the outward with myself the only passenger on the return.
But base an airline in Wales, employ a workforce in Wales, take the government subsidies, but branch it out, there are niche routes begging to be served out there by aomething like a Do228 operator, the CWL/VLY/CWL route for one, back in the 90's Air Kilroe commenced a MAN/CWL/MAN route with a J31, people were laughing but the passenger loads were good, probably for connections in/out of MAN, the IOM ticket seller apparently made a successful route with IOM/GLO/IOM, IOM/BLK/IOM is another route currently being neglected, IOM could also do with a morning & evening puddle jumper service to/from BHD, Waterford needs such a size of aircraft operation, perhaps WAT/BHX/WAT, maybe a niche route or two to be had out of LDY and the list probably goes on.