When you say restrictions on the size of acft that can be used, what do you mean? There'll be no regulatory restrictions, but there may be runway restrictions. Is this what you mean?
I don't think runway length is a major issue on t/a flights; even an A340-300 can fly most routes from DUB and the -600 would have significantly better performance.
I do think, however, that if EI isn't ready, it's a market ripe for the taking. It's a potentially very good market, held back only by internal political considerations, so once those shackles are removed and if the incumbent carrier isn't in a position to take advantage of the opportunity - through a combination of a poor service product and not actually having sufficient aircraft to operate new routes, other airlines will be watching.
I feel that it is most likely to be the small, dynamic private companies which will jump in, rather that state carriers like AF (although it might well be possible that Cityjet would wet lease some AF A330s/340s?)