I think it would be better for all involved if bmi was to leav altogether. I say this because at the moment bmi are stopping other airlines from starting routes into London, I don't mean there is an agreement, just that at the moment they are providing enough competition to make airlines think twice about doing flights into London.
I think what would be better now for MME is for someon like Flybe, Ryanair or Globespan to do a twice daily Gatwick and for KLM to go to at least 4 daily on the AMS with F100s. This would then cater for the London area traffic as well as providing decent connections (through AMS) for onward travellers.
I think now 'open skies' has been agreed the government should step in and allocate slots into London on some sort of basis. It doesn't have to be all into LHR but as long as each regional airport outside of x miles of London has some sort of link. Just an idea though.