Kurt, I finally had an opportunity to try your procedure on a sensor for a friend ( I don't have a TPMS on my trike).
I used a heat gun to warm up the sensor and it was easy to cut off the cap with a utility knife.
I had no problem breaking the spot welds on the top of the battery, but although I heeded your warning about not lifting the battery too high, the solder let go on the lug. I soldered it back on, and it seemed to hold pretty good!
I installed the battery and proceeded to glue the cap back on using JB Weld Plastic Weld for Rigid and Semi Flexible Plastic.
It is an Epoxy Putty that you knead. I rolled into a worm like shape, and set it into the sensor joint and held it together in a vice!
What I didn't realize was that the joint had to hold air pressure...
I probably had a void at the point where the epoxy rope met.
The good news is, the sensor worked when we tested it. It was showing 41PSI.
The bad news was the pressure was dropping due to a leak in the glue joint.
I think it's a simple fix! I will remove the cap and re-glue it after cleaning it up.
I will likely use Cyanoactylate Adhesive (which is what Permabond 240 is). I can't seem to find Permabond 240 in Canada!
When I complete the fix, I will report back to you!.......Marcel