ShotOne
I don't get your point. Is it not the same as what presently occurs in Dublin where Lufthansa, KLM and BA (albeit IAG) nightstop and grab Irish originating pax then fly them to a hub and onwards? None of the aforementioned airlines have bases setup in Ireland nor employ local crews. The most they would have is perhaps a country/regional manager and use third party service providers for ground services. This is all enshrined in the various "freedoms" of aviation.
EI are employing local ground and CCMs in MAN and there is provision that if the base is under subscribed for flight deck then EI UK can go into the market and hire directly.
If you want to get a flight deck position in Aer Lingus UK then I am afraid there is no way to skip the queue as there is a seniority list.