A server queue would be nice, makes the process of joining a full server be more fair and less about which person gets lucky and spams connect at the right time.
I think there's enough official servers for the demand (maybe one more siege server), but I have noticed a problem that when one of the battle servers gets filled, people would rather wait for a spot to open up or go play something else instead of going to the other, empty server (which might actually start to fill up if everyone just tried).
Same for naval, there are usually a lot of NA players on the EU naval server because the EU server already had people in it so the NA server just remains empty.
Could maybe use something where you pick the game mode you want to play, and if there's hardly anyone in the queue for the full server, it puts you in the queue, but if there are a bunch of people in the queue it puts them all into the empty server (the server browser would of course still be available if you want to join that specific server). Of course, it's hard to decide how many is enough, because some people would be fine with only 10, others would want maybe at least 50, while still others would only be satisfied with 100+ (these people should probably just put themselves in the queue for the full server).