Considering the sheer amount of cool sets already implemented on MTGA, it would be great if there were two Quick Draft/Premier Draft queues available at all times: the most recent Stardard set, much like it is today, and a Historic set (perhaps rotating once every two weeks). I'm sure your internal data will confirm that there are enough Limited enthusiasts to ensure those queues will be consistently filled without long wait times. Presenting an alternative will also mean that those who don't like the current Standard set or those who have already explored it fully will now be more likely to pay the fee to enter the other queue rather than wait for the single set rotation, and certain crowd favourites from among the Historic sets are bound to bring a boosted audience to the format.