Freeze MMR option
Basically with this option ticked, you queue on ladder at your current MMR, but you can neither gain nor lose MMR.
We already have casual mode, but the queue times there are long. With this option you get to experiment to your heart's content in a low-queue time environment, without risking anything. Only possible problem I can see is that people could conceivably boost each other (one queues with option ticked, the other without, and the first player throws the game), but there's the banhammer for that.
Basically with this option ticked, you queue on ladder at your current MMR, but you can neither gain nor lose MMR.
We already have casual mode, but the queue times there are long. With this option you get to experiment to your heart's content in a low-queue time environment, without risking anything. Only possible problem I can see is that people could conceivably boost each other (one queues with option ticked, the other without, and the first player throws the game), but there's the banhammer for that.