This is nothing to do with numbers, or making a "super" team. There is little distinction between those players that live in Walsall and those that live in Birmingham. In fact, a lot of people would argue that they are one in the same catchment area as far as the APAT online league goes. This therefore made logical sense to create the West Midlands Poker club, as a lot of the Birmingham players were suggesting that they would play for Walsall, as it was just as close to their home.
Liverpool and Manchester is a different situation. There are two distinct catchment areas within two large cities. Very few players are going to suggest that they could have joined either when it comes to the league.
We always knew when the clubs were setup based on casino locations, not all clubs would generate large numbers, but with the shut down of both Bolton and Blackpool, I would expect both Liverpool and Manchester to pick up some players aswell.