The current issue with NA/EU servers, when it comes down to it, is quite simple: there are simply too many people trying to play at the same time. The fact of the matter is, the existing 25 NA/EU servers are basically already near, at, and in many cases, over capacity.
Assuming most Early Access players stick around for official release, the influx of new players joining at that point will almost guarantee the necessity for new servers to be opened up. There is no other way to address this. No queue or server maintenance will resolve the fact that too many people are trying to get in. Yes, eventually the server populations will most likely stabilize, but it will come at a cost of many people having already left.
Meanwhile, the Japanese servers are humming along relatively problem free. This is not because Japanese servers are somehow better, but the result of a simple marketing decision to "designate" these servers, which are physically located in Japan, as "Japanese worlds".
The reality is that the latency difference between a JP and a NA/EU server is mostly negligible for most people. In fact, I'd wager if Square Enix never bothered with separating the servers and simply stated "we have 50 worlds for all players in the world, feel free to join any one of them" we would have a far more even distribution of players across all worlds, and you won't have this issue of the JP servers being underutilized while the NA/EU ones are bursting at the seams. And I would bet nobody in NA would even notice the latency difference of a JP server (and vice versa).
My solution to the devs is to abolish the system of "designating" servers. Simply list ALL servers in a single list for ALL world players. All servers would then be utilized evenly AND you end up with the benefit of a more varied world community that people valued in FFXI.
For now, there needs to be more servers. Once that is done, please allow all existing players to do an optional one-time server transfer to ONLY those new servers, so those who wish to reunite with their friends/family or are willing to leave their current world for a less congested server can do so.