The same question can be asked : what would do a WRC driver on the track compare to Schumacher ?? Certainly not bad but not as good, as Schum would do.
Being a track driver doesn't mean you can't drive sideways, just look at Tiff Needell, he's a track driver (F3, F1, LeMans ...) but i would certainly thrust him, being chase by criminals.
Mikka Hakkinnen drove a rally car on snow/ice too last year and he wasn't bad.
Also Stéphane Sarrazin who was a Prost GP testdriver finally decided to go to french championship rally and he's the leader now.
Alain Prost raced in the ice championship (Andros Trophé) with great success this winter (finished second) and so ....
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