As I see it, Bristol has every right to get annoyed with this. Cardiff Airport has failed due to systematic poor management, poor investment and a limited catchment area. Forget diluted borders....this is a private company we're talking about that is in direct competition with Bristol - and they could be about to get a significant tax break as a reward for their incompetence.
Bristol Airprot (and BHX for that matter) has generated countless millions for the whole area's economy (Wales included) by capitalising on being successful, yet they would be heavily penalised in all of this - thats a kick in the teeth for their good management and investment!
To put it another way, would the Welsh Assembley also reduce taxes for Tesco, as the Sainsburys up the road is doing that much better?? Its absolute tosh, and an insult to anyone that pays their share of tax to the state.