CWL also needs a decent low-cost airline like EasyJet too. That will bring in the crowds, they'll spend more, infrastructure can be expanded, which in turn will bring down the airport running costs.
I use BRS every week or so for business, and they really are forging ahead of CWL with huge, modern security check systems, soon to be opened large number of e-passport gates, 30+ gates, constant bus links into Bristol or surrounding area, loads of parking space etc. They reckon they'll be handling >10 million passengers annually in the next year or so, and it shows. I fear that CWL will never catch up.