Have you ever actually seen these systems in person? It's usually a microcontroller which already rules out a ton of stuff you're talking about. Serious places will buy 2-3 of them at the time of installation to have some spares. The ones here are "user-replaceable" as well (unplug these three cables, replace the box, plug them back in). It's not some mysterious bunch-of-wires-on-arduino-pins magic box that nobody dares to touch.
The one at my previous office even had centralized management through an RS232 connection to a PC. No internet and related downtime at all. And I don't recall us ever being locked out because of that.
Have you ever actually seen these systems in person? It's usually a microcontroller which already rules out a ton of stuff you're talking about. Serious places will buy 2-3 of them at the time of installation to have some spares. The ones here are "user-replaceable" as well (unplug these three cables, replace the box, plug them back in). It's not some mysterious bunch-of-wires-on-arduino-pins magic box that nobody dares to touch.
The one at my previous office even had centralized management through an RS232 connection to a PC. No internet and related downtime at all. And I don't recall us ever being locked out because of that.