I think DUB will get this flight.
I cant speak for BRU, but MAN already has a flight to CPH at 10:15, and CPH is twice daily. DUB is once daily with an 18:00 dep to CPH.
Unless they jiggle the 10:15 dep at MAN to a bit later, and make MAN 3 daily, it wouldnt work otherwise.
Those are the only 3 airports in the running, so like I say, my bets are on DUB.
As for EY cargo, how restricted would their B773 be? I know they have already used it at DUB, but Im not sure if any restrictions were in place. Could their B773 not be used on the route to suppliment cargo also, as its the main reason MAN was upped to the B773 and not receive the frequency increase like DUB.