Would it be an option to add something like a soft geofence? A double geofence where the first layer can be set to RTL (or land at rally point) and the second to perform a land, terminate or whatever else is deemed the safest option.
We had an issue during manual test flight where the control surfaces stopped working. Still working on the RCA, but seems like a sketchy UBEC on the servo rail is to blame. The VTOL craft hit the geofence and tried an RTL but of course couldn’t. It was manually transitioned and brought back, but that is a nice failure case for a fly-away. (I never like manual flying anyway, but sometimes there’s the need for tuning).
This is also something with a relatively high likelihood of occurrence and definitely a high impact in an FMEA term of things.
Looking forward to your thoughts.