Now that’s an excellent idea
Only joking !
But to be fair they’ve done exactly that twice since the war, around the Bullring and Digbeth bits, and they’ve just swept away another huge chunk of city centre for HS2. That’s a lot of remodelling of a city!
I suppose that depends if you consider the mess that is/was Digbeth part of the city centre or not, and quite a lot of the Curzon St footprint was derelict anyway, even the platforms were still there. I guess it's a bit like somewhere like Ardwick in Manchester - it's not the city centre now, but in due course it will be. You'd need to flatten some attractive old buildings if you wanted to put a Manchester Piccadilly style concourse on the Stephenson St side, which is where it'd have to go as that's the side with most demand. You could put one on the other side where the demolition would be of fairly manky buildings, but then it'd be less convenient.
I suppose at a push it could go where TK Maxx is, but it'd be quite small then.
You could certainly, looking at an aerial view, do two bridges under a nice trainshed, but then the retail offer would be significantly downgraded, and to be honest the retail offer is one reason I like to change there. I'd not want to change it into Bristol Temple Meads - a lovely trainshed but hardly any retail at all and nothing near it either.