They could own up to 49% of the airline, but no more, same with Ethiad or any non-EU carrier. B6 have already discounted interest in mergers, I believe. UA are going through integration of UA into CO at the moment, so can't see them being too interested either.
That's true look how much control Delta has at Virgin with 49%. Didn't Aer Lingus say flights to the West Coast in Summer 2012 would not return due to predicted losses only to announce 12-months later a return, businesses change everyday - so ruling out something is never long-term. The United/Continental merger has been completed for over a year now? The only things remaining being the repainting of aircraft and branding at airports.
their experinece with bmi would suggest they have little interest or appetite in this market.
You seem to forget to point out how troubled bmi was before being purchased by Lufthansa. They simply put the wrong CEO in place to deal with the mountain of problems bmi had, if you want to point fingers for its failure I firmly suggest you start with Sir Michael Bishop.