Saudi Arabia is now e-visa entry for UK passport holders for tourism visits or I've heard visa on arrival. Saudi has hugely loosened it's tight grip on inbound entry to try to boost tourism. With the attractive fares to a variety of Mid East and Indian sub-continent destinations being offered from BHX by Saudia + free stoppers in JED, I think Saudia will do (eventually) well out of BHX
Is there enough room for Turkmenistan as well as QR, EK AI and SV yes I think so, as long as they restart ATQ otherwise I'm not sure as that's the connecting traffic the route survived on - AI and T5 co exited at BHX before so I think there's still room for both