Agree and your approach would certainly work. I have another idea I want to test though. I suspect the issue is that when I connect the ICSP header, to the board, the Vcc from the header will energize the other devices and bring the i2c pull-ups into play. So, I am thinking I will put a Schottky diode between the watchdog and Vcc. That way the ICSP will only energize the Watchdog.
I plan to do another OSHPark run so, if my somewhat crazy idea does not work, I will implement jumpers as you suggested. I am trying to do all the Watchdog stuff under the Particle device so not much clearance there.