Attitude already comes from the IRS in aircraft so equipped. Gyro is only the backup (standby attitude).
Airspeed and
Altitude must be referenced to the
actual atmosphere being flown through. You're flying through air, not space. Spacial reversion is the backup already (BUSS/GPS).
The issue is recognising an instrumentation problem, and being able to ignore the suspect data and revert to backup source.
You're right though, some fresh thinking is probably useful!!
