I don't believe the chemistry changed. Do you have any reference for that? You can bypass the battery and drain the coolant so there is nothing to leak - but you lose battery conditioning. You can try to implement the fluid detector idea we've thrown around, so you can keep battery conditioning and ...
The likelihood is that when you open it up, there won't be anything that looks damaged aside from being wet. It won't be until after emptying and drying it that you can determine if there are further problems that aren't immediately visible. But at that point you can pull codes, knowing that whateve...
Honestly, it could be a bug that never had the chance to appear before now. It probably doesn't happen immediately when connection is lost, but I doubt the software testing included weeks/months soak without a connection.
I can't confirm, but I will tell you it tries to update the time using the cell network. While AT&T killed their 3G service and the SIMs were deactivated, it was likely still able to see towers/cells nearby and that may have finally stopped in your area.
There are a few folks dealing with battery issues right now. Depending on what gets bought, it may be possible to get more than one vehicle fixed - but folks will need to coordinate. Users that have noted battery issues in the last 2 months: Aidensmccormick, Bradleydad, Robonthecob Eltonmalone, Ains...