BHX
Whilst of course more than feasible operationally to serve more European routes from other bases like MXP, LYS and TXL, it's a prospect that seems quite unlikely.
It doesn't really suit their usual network development strategy in the UK and would still be hugely limiting as to what route development opportunities could work from BHX.
If there was a significant appetite to grow a European route map from BHX, they'd open a base, pure and simple. The problem right now no doubt would be access to optimal first wave slots, but they wouldn't just serve odds and sods from other existing bases as a substitute to more profitable expansion, simply just because they can.