It's blatantly clear that easyJet can make more money elsewhere, which is why (in my opinion) the airport need to try and find a carrier that is actually going to serve the local area and economy the way it needs to be. Such as, I hope Eastern and Flybe come to an agreement to serve NCL-BHD with a few daily flights, because the easyjet schedule isn't amazing there either. At least day returns are possible though.
Knowing the south west, how awful the traffic is and (at times) how badly connected places can be... By the time you've paid £200 for NCL-CWL, got yourself into Cardiff, then into Bristol and to whatever your destination is (or paid the best part of £100 for a taxi) I'd rather spend £60 on an easyjet flight and £39 a night at premier inn, or splash out £60-100 for Hilton/Mercure... You're not making your 9 o'clock meeting in Bristol, by flying into Cardiff. You'd be pushed to get there for lunch!
Unless it is on a Monday, a day return to the south west of England is impossible by plane and implausible (and prohibitively expensive) by train. You could drive... But there's 12 hours of your day gone.
Bmi regional offer very reasonable fares of £49-69 one way on similar length flights across their network, and a very efficient, friendly and welcoming service I for one will be keeping my fingers crossed.