I would imagine that the executives at COA and AA would have the resources and expertise to thoroughly research the market for potential routes and take into account such factors as presence and success of low cost carriers at the target base, car parking, facilities, transport surface access etc. With the explosive growth of pax numbers at one of the Uks major, regional airports (if I might use that phrase) in recent years along with the considerable investment made in passenger facilities, any proactive airline with a mind for seeking out business opportunities would be very interested indeed to examine the potential. Despite less than adequate transport links BRS does have a very large catchment area indeed which CWL could never hope to match.
The business community in the SW would wholeheartedly welcome any alternative to having to trudge up to London if the option was there and the experience was reliable and dependable (which with the advent of CAT III at Bristol I'm sure it will be.)
To quote an earlier post I believe it's a case of 'not if but when', you'll see a scheduled BRS-USA route within the next 12-18 months if not sooner.