Phileas,
Yes - very good points, but MOL also really loves a bargain - and has said before that airport fees will drive route selection more than anything else.
However, I will accept FRs recent trending has been towards larger airports - as also happened with WN when they reached a certain saturation level with the cheaper fields.
So you could factor in an average £30 yield at CVT might be £35 at BHX. But one thing we do know is that if you piss MOL off, he will go elsewhere.
Hence I still ask the question about what is and isn't technically possible. Even TOM didn't do Greece, and iirc no Canaries either. My concern would be that even if, say BVA and CRL were technically possible with a full load, Coventry is close enough to London for Eurostar to be a better option.
If South France or GRO / REU are reachable with a full or near-full load, maybe its an option.