So what did you do when those devices broke for years while you had no local/physical person on site? You either didn't need to employ the person bad enough or didn't need the devices to function bad enough.

Engineers aren't cogs, but they are able to travel and you can hire them by other means that full-time employment. So I suspect that was probably what you were meant to do for your situation.

Nothing about this was mission critical or even all that important or you would have found a way to solve the problem or you did and it wasn't a problem to begin with. I'm in a field where people often want to hire me for some special thing like this, but it often turns out, most of my life would be spent idle because no one company has enough demand for me. I can consult instead and be busy all year, or I can take a job for someone that's OK with me being idle for 80% of my time. I prefer the former for multiple reasons but just making an example of why hiring for specialized roles that aren't mission critical is often not the thing you should be doing.