IMHO I see 2 choices.
1 Cancel APD in Wales, if they can persuade central government to give them the powers. This will attract the 2nd tier transatlantic (like TCX and TUI and MON) carriers who are hurting badly from APD.
2 Plough it up and build a housing estate. BA can go to St Athan and it will employ a couple of thousand building workers for a few years.
Most likely outcome, more fudge, delay and ineptitude at which the Welsh Assembly are masters. Can't wait to watch it all come falling on them from a great height!
Any bets the Spanish will walk away with a sackful of our hard earned tax revenue?