That was my unintentional strategy, lol
I bought a Rize X (750 hub fatty) as a starter bike last spring because it was available without a wait. I pre-ordered an RX Pro for September Delivery. I had planned to sell the hub after the new one arrived, but in the end I kept both and have set up the RX Pro as my commuter, and use the X as my weekend cruiser and townie. The RX Pro is fantastic for my long commute (40kms return) but just barely gets it done on one battery in summer. Cooler weather requires 2 batteries or a charge at work as I burn 60-70% each way with high assist - between 3-4. Range on the X is significantly better for lazy unscheduled Sunday rides, between 80-100kms, and the hub is powerful enough for city cruising if I avoid the monster hills.
I am thinking of grabbing one of those 25ah batteries next spring to try and get enough of a buffer on the RX Pro that I don't need to carry the second battery to work. I also agree the new 30ah dual battery options would be appealing on an Ultra since they are such battery hogs. Weight starts to get nuts though...
And I can squeeze 100kms out of the X with moderate assist settings, so with the 25ah battery on that bike, I suspect I could possibly eek out 130+kms. That pretty much exceeds my butt-hour capacity anyway. ;-)