Possible. But if that were the case, i think they'd both be restricted to complete base. no sharingan, no kyuubi, no sm, no summonings, nothing to keep it fair for the other genin's in the exam. Doubt that restriction would change when their time to fight would come considering the hosting country won't want to lose their arena. That'd like letting hashirama and madara loose to fight in your village - complete idiocy. :/