This seems fairly obvious, but I think that the belt (or even BP queues!) could really help the game out for the quest release. I had an idea that there would be a bunch of white belts all learning together and fighting together, but that only really works if they can queue into each other consistently.
In addition, experienced players are
really
getting fed up with having to fight lower belts when they just want to fight blackbelts, which is fair enough when they've been doing it since the rock cam got released.
I doubt that rank queues would be too difficult, and the matchmaker looks kind of empty without those queue options, but I think it should definitely be added to allow for the greatest enjoyment of the game, from new players to old ones.
If you're planning to/already have re-added the queue options, great!