Twin aisle
The WAG to the best of my knowledge do not have devolved powers over APD, what has killed CWL is the current fuel price and lack of wealth in the catchment area, that not to say there isn't money around, just not enough people with it to make a year round jet operation viable.
BRS enjoys a critical mass in terms of airlines and destinations served and of course a far larger catchment area. Scrapping APD would make little change to CWL fate, the days of 9.99 tickets to EDI are over. Whilst scrapping APD on say long haul route where the planned ramp up of charges is greatest may tempt a few fringe airline, the lack of a Cat3 ILS would deter route planners from a 5.30am arrival. With the best will in the world i can't see it happening.