This is a little unfair - and I'm not from BHX, don't even much like the place - for the following reasons. This was discussed in another thread called, I think, Heathwick, not long ago.
BHX has a lot of spare capacity. It's catchment area is huge, and if they were to build HS2 it would be very easily reachable from the west side of London. If the UK had a joined up transport policy and was not Londoncentric, BHX could work as a major hub.