Is this a back door method of EI taking over AA in the long term?
I doubt it to be honest. As has been mentioned in previous posts Aer Arann take all the risk. Aer Lingus receives a franchise fee from Aer Arann for operating under Aer Lingus' brand name. In return Aer Arann receive the monies from passenger bookings.
Aer Lingus don't have to pay for staff, pensions or aircraft maintenance. So I can't imagine EI wanting to take over RE.
Maybe someone else has a different view on this though.