Question to a developer, why not make it so that when a GPS signal is lost in RTL mode transition control mode stabilize?
Because of the loss of GPS signal recently flew a quadrocopter. After enabling RTL for the lost GPS copter gained altitude of 200 m and left in an unknown direction.
The APM try to make its best to circumvent difficult hardware situations, and version 3.0 will add a couple enhancements here and some checks before arming, but obviously it is often impossible to fix a hardware problem with software during flight. Copters need strong mechanical and electronic user checks before flying and rigorous parts changes periodically (in our case mainly motor ball bearings).
Failsafe and RTL must be considered the last resort.
Anyway If you have radio control it is easy to change the mode back.
Without radio control we need to rely on the APM and in this case it is mandatory to decide a failsafe action as soon as possible, depending on the failsafe source and available sensors the safest action is decided, with an emphasis on ground people safety. Getting back the copter become less important in situations where radio link + GPS are lost.
We can't wait when a failsafe do occur. Generally the more you wait, the more chances to crash.
Version 3.1 should have another radical failsafe option, but that's another story. (it's not self destruction :)