We've been thinking the same thing for our outback trips here in Iceland.
We have good backup from people traveling all the time in the Icelandic backcountry. There's this popular thing here which is driving cars on glaciers (I'm not kidding). It's modified 4x4 trucks on 38 to 52 inch tires, there's thounds of them here in Iceland (population only 315.000). This link might give you an idea:
http://www.arctictrucks.com - have a look, its awsome. This is a local 4x4 modifycation company which went with the british Top Gear TV show guys (snowkites appear on the show - race to the magnetic north pole).
Snowmobile trips are also popular.
What I've been thinking is either changing my car for big wheels (expensive) or keep using my unchanged Landcruiser 4x4 and a trailer/snowmobile (also expensive but a bit cheaper).
We have different elements to prepare for: Weather which can change to a whiteout in minutes, cravasses, escape plan etc.
On general notes this is what we do before leaving home:
1. Leave a travelplan (where - when back).
2. Some communication device which works on location (some of us even thinking of partnering up for an Iridium phone)
3. GPS and a map and always a low tech compass (GPS rely on batteries, some spares of course)
4. Knowledge of the area - possible cravasses and other hazards
5. Knowledge of survival techn. such as snowshelter building
6. All weather clothes (3 layers)
I'm probably forgetting something important, but apart from all that we have volenteering rescue squads which are available 24/7 all year long (equipped with monsters jeeps, snowmobiles... the lot) aswell as the national rescue service (helecopters etc.)
The funny thing is that with our kites and gear we are probably better prepared than many guys traveling on snowmobiles and 4x4 trucks. Many dont have any GPSs and no form of communication devices.
I'm maybe going off track here but this is our senario and I've been thinking exactly the same regarding snowmobiles. I've also been wondering if the 4-stroke once might be more reliable. I've had a 2 stroke jetski and with those engines it's not the case if they brake down, but when. With 4-stroke I'm thinking you might be getting the same reliability as enduro bikes or cars. More expensive though. I don't have first hand experience with them - just a thought.
One thing I've noticed watching enduro bike comp. on TV is that they have a harder time starting the 4-stroke engines after stalling them than the 2-stroke ones.