Well, in case, with their respective main positions, some of the biggest possibilities for Arsenal's lineup for their main lineup will be like this:
Possibility lineup by transfermarkt
If they can't get Merino, it's fine. Possibility lineup by transfermarkt
But they must able to get Gyokeres, I see that he's really a good player, he can perform when he play for Coventry City and Sporting CP. Although he was failed in Brighton, but he's keep improving himself and build his confidence, he's already in prime.
It's a big loss if Arsenal can't get him.