Equally possible to run the companys as completely separate companys........ BA Gatwick / Heathrow T&Cs are a prime example.
Indeed with Mixed Fleet at LHR now on less than LGW(!)
Aer Lingus long haul and on city main airport routes and Ryanair on everything else with Ryanair being used as a feeder service for LH Trans Atlantic.
NOBODY on God's Earth is going to fly Ryanair to connect to Aer Lingus out of Dublin on long haul. The only thing worse than a normal short haul connection at the end of an overnight transatlantic flight would be if it were with Ryanair. In all seriousness, even on price, I think that's a step too far. MOL does NOT do complexity, one aircraft type, no sophisticated booking, cheap as chips, no connections. The FR culture would get f***ed up overnight the day they did that. They dismantled Buzz for a good reason, Aer Lingus in the hands of Ryanair would be....er Ryanair in a year. A for long haul, well in all seriousness it's only six aircraft and one on lease to United. The real win win would be decreased competition and massively increased yields out of Ireland.
Eire is not nearly as competitve as London, hence this is not like BA buying out BMI.