I'm pretty sure that Disney has a "Star Wars Quota" that FFG has to meet each year to keep the license (brand visibility and all). That would explain the sheer level of (great) content it receives. But I don't think they dictate each ship.

I think part of the second wave of Armada Fighters, along with the Rouges and Villians set, is an alignment between X-Wing and Armada. We see that in similar card abilities (Biggs in both games) and in ships (Imperial Raider, Gonzati, Rebel Transport). It is almost as if FFG is a Star Wars Universe, so once its in, its in.