US Visa regulations were recently relaxed for Eastern Europeans in the EU and there is now a whole new market there to be exploited. My guess is that AerLingus will be looking to link up the Bucharest, Vilnius and Warsaw flights with the LGW-NYC route.
But that could already be done through Dublin and you could get security vetted before even leaving Europe. I'd say that's a risky plan of action. It has to be a route that appeals to the local crowd at Gatwick. I think attracting the Irish crowd via Gatwick is the best plan. Maybe hooking up with an Asian carrier with a desireable destination there with links to Australia would be a sure bet I think. Maybe a carrier in Thailand for example?