There are two options for BHX to expand that are realistic and foreseeable in my opinion. First being expanding the what I'd call Flybe Terminal out further on the ramp, adding a few stands with a direct connection to a terminal, rather than the run across the ramp malarky that can cause issues.
Personally, I still think BHX's best chance at an ambitious expansion that is still realistic would be building a new pier on the space where the remote stands currently are.
To connect to the main terminal a bridge over taxiway victor (like at Gatwick) would be much more cost-effective rather than building on top of and therefore cutting off taxiway Tango.
If stand space was still required not connected to a pier, the section of grass area next to taxiway Tango housing the 'Low Brook' could be very easily converted to remote stands. The Brook could be very easily diverted to the left of Tango instead. Or flow underneath in a pipe.
All the calls for 'Build 20 new runways' or 'Build 5 new terminals' (Exaggerating obviously) I feel are unrealistic for an airport at BHX's current position in terms of annual Pax count and Runway 33-15 is no-where near at full capacity.
The obvious options for expansion are right on the airport's grounds, not miles to the south or east. But they seem oblivious
That's just my opinion though...