Disconnecting batteries

Yes. The engineers have devised all kinds of problems that will force you to get it back to the dealer to have things reprogrammed or unlocked. None of this benefits the owners. A better idea is to connect a small solar charger if there will be light during the day, or a small trickle charger. You can set that on a timer so it doesn't have to run all the time. A little 2 amp charger that runs a half hour per day will be plenty to replace what the computers' memory circuits draw. I'm happy you thought of this before you disconnected the batteries.

I don't think it would be a big issue at all. My shop is in a seasonal retirement community and my customers do it all the time with good results. The computer will lose it's learned memory which includes radio stations, seat memories, fuel and idle strategy but it will relearn the strategies right away. You'll just have reset the radio stations.