In the cases above, the ECU isn't malfunctioning, it is doing what it was programmed to do. A different ECU box would react in the same way.Why not just mount the ecu in the cockpit, if it goes tits up swap it for a new one?
The limp-home mode in factory ECUs is designed to protect the engine when a sensor input is out of limits or missing. In a car, it is an inconvenience. In an airplane, the available power under limp-home mode might not be enough to remain airborne. So, maybe it should be called "limp into the trees" mode in our case.