Interesting scenario.
Please remember the G1000 (and other Glass pannels) are NOT one system. Just like flights instruments (clockwork) are NOT one system. But they have connected parts. So the whole system does not just fail.
e.g. Each Pannel on a G1000 has independent GPS, Radio, VOR and Fan's.
You need to look at failure as you would for normal instruments (e.g. vacum)
This is likely to be:
AHRS (only one!) - use backup AI and Mag compass
Pitot - (only one - normally) all airspeed use GPS + feel when landing
Audio Panel (Radio should auto set 121.5)
Single Panel (Reversionary mode) - Minor issue here is loss of moving map but still have 1 GPS , 1 VOR and 1 Radio (or two if some wierd fault)
Fan dead - shut down the appropriate panel - then as above.
If you cant get there before the battery dies or smoke (fan dead but you didnt know) then im with IO - get the backup GPS out of the bag and portable radio.
(I've often wondered how good the ones with VOR support are?)