Maintaining the car as per Subaru means 0-20 oil. If you have engine related issues with not even a single mod, you'll be required to provide maintenance records. A receipt with anything other than 0-20 and you're stuck with a bill.If he maintains the car per Subaru (un-modified) why would there be a concern about warranty claims? I sure hope a car like this can handle some snow donuts and a few stop light races. I'd have no issue buying one for any of my 3 teenage boys or a GTI, Civic Si...cars in this class.
As far as "snow donuts" is concerned, it's the quickest way to kill a Subaru. Oil will flood to that side head and you're done. You track, talk to a few Subaru owners. You'll need a kb pan and pickup at minimum for tracking on anything but 400tw tires. Don't even talk about prolonged turns.