The only one that I think sounds reasonable is #1. I'd bet there are hundreds of customers with WBO2 sensors permanently connected and flashing with no issues. For sure if there was an issue I would expect to know about it With the LS1 controller as well the PCM "should" really only be killed during the first few seconds (bytes) of a full-flash where the bootloader code is written. A cal only flash that fails should be recoverable.