cool stuff they have over there!
your project sounds sufficiently challenging, but not so much as to be unattainable! I look forward to hearing your progress!
back when I was flying model aircraft, I built a similar rig in one of the club's trainer airplanes, using the mercury switches as outlined above to maintain a "sane, level 'holding pattern'" in the event of operator panic (use the 'barrel roll' switch on the 7-chan transmitter) or loss-of-signal -- the plane would fly figure-8's and circles at what it thought was between 150 and 300 feet above ground level. I used an 8051 microcontroller, recovered from an old IBM PC keyboard. The toughest part was getting a somewhat useable (I won't say accurate!) altimeter... probably the most expensive part of the whole thing, really. it was just a barometric sensor, and you'd have to "teach" the 8051 where 'ground level' was just before taking off.
I didn't do the project to save any expensive aircraft (it was only ever installed in an ARF trainer!), but really as an exercise to prove it could be done. 