So you let the thing run and brief the other on what to do if SHTF. We're talking hundreds of units out in the field, not millions. Every aspect of that can be provisioned for ahead-of-time, and cheaply at that, and then the SWE can walk away for weeks at a time.

If the HWE leaves for a bit, same thing. If he's making units production stops, but maybe the SWE can fill in since these dont look like difficult builds.