IMHO, from a purely business perspective, EI offers nothing to IAG other than the Heathrow slots. Also only two airlines currently offer DUB-LHR services and from a completion perspective allowing them to merge would be just as anti-competivie as a take over of EI by FR.
But you forget that for EI its NOT FR so its acceptable and isn't WW one of their own so they will say its safe in his hands .......................never mind that Cardiff easily accommodates all heavy maintenance and admin functions can be anywhere.
Mind you I can see Ryanair selling on the shares to IAG relatively easily and reckon MO'L will have a smile doing so as well.