You can (and probably will) say, well if that's the case, how do they make a success of Manchester? In my opinion this is down to the ease of access from Birmingham and East / South Midlands to the two major LoCo hubs of Stansted and Luton - both of which can be reached by road in less than 2 hours making them attractive points of departure for Midlanders, who, unlike the enthusiast has little interest on flying locally, but more in the available fare.
An excellent point ATN - just as an example, three of my colleagues at work have separately booked to fly from LTN with EZY in the summer, respectively to Nice, Rome and Barcelona, all of which are routes available from BHX in S12. The reason: price, EZY fares were cheaper than foing from BHX. And living in Leamington Spa, Luton is not that far for them to get to if no traffic on the M1. The central location and ease of surface access to BHX is IMO actually its achilles heel, as it makes it also a very easy place to get to other places from!! Never say never but I just can't see EZY setting up a base at BHX in the middle of four established bases (LTN, MAN, LPL and BRS) all of which are easily accessible from different but substantial parts of the BHX catchment area.