I really like this idea. I'm sick and tired of buying over $200 worth of tires every year just to keep up with the latest fad. Just to end up with something that's marginally better than last year.
Problem I see with applying this to offroad is the inconsistent track surfaces and materials from track to track. In the past I've needed 3 different sets of tires to race big events like the winternats because the track changes so drastically from practice to quallies to mains. And I'm not talking foams here. It was bowties to crimefighters to holeshots.
I don't think this would work with one spec tire. You would probably need 3 different spec tires. Even this would be a huge improvement over what we have to carry from race to race now. Never mind yearly expense.