AWD doesn't have more traction in the situation mentioned, i.e. taking a turn too fast on an icy road with chains on. That AWD myth (mostly due to false marketing) needs debunking. The only time AWD helps is when the vehicle is accelerating by providing 2 additional wheels of drive. For example, driving up an icy hill where 2WD might not be enough. However, AWD is useless regarding entering an icy turn too fast in which case you'll be braking not accelerating, and the traction at issue is controled braking and lateral slippage.
If one is a stunt driver and can fishtail and then accelerate out of it.... maybe AWD matters, but that's extremly reckless driving anyways and not reccomended. Also, unless it's a Subaru or other low height AWD vehicle, it's risking roll over. The poster mentioned Subaru Outback which is one of the best AWD vehicles becasue it's also low and has relativly large tire/pavement contact patches relative to vehicle weight, unlike most SUV or pickups. For serious snow/ice driving I'd reccomend a Subaru, lower the better, and importantly: with VSC aka ESC.
Tires do matter on icy roads, but winter tires can be put on any vehicle for equal effect. A big AWD SUV may look impressive, and they're marketed like crazy as being rugged and such, but in reality they're only better at snowplowing, real offroading, and going up steep icy roads. On ordinary icy roads like the turn mentioned above, they get no better traction at all, and in some ways are worse due to rollover risk. Chains negate whatever type of tires are underneath pretty much. Some chains are better than others though.
VSC (and to a lesser degree just antilock brakes) are the only technologies other than tires that will help in the above loss of traction situation.
About VSC retrofits, if the poster really wants to know, and assuming this topic isn't a troll, obviously the dealership would be the place to ask, but I'm pretty sure the answer is no on retrofits. I'd reccomend putting on snow tires next time and just driving slower.
Btw, I recently deliberatly engaged the VSC on a wet and leaf covered downhill road by braking hard and manuvering slightly, just to test it without taking any risk. After a couple preliminary tests starting @ 20mph and gradually increasing manuvering, I got it to engage very breifly at about 40mph with a slight manuver. It was beautiful. VSC icon came on, anti-locks activated, and the car never deviated from the desired steering input. Sweet. I felt confident it could have been pushed a lot further than I'd ever want to deliberatly.
Of course I wouldn't push it on icy roads with high speeds, or sharply turning freeway offramps in the rain and such, it's not magic afterall. But it did greatly increase driving confidence to know it works, and it's there to correct some amount of driver error or enhance emergency control.
