IMO, I think it should be made so that you cant change your deck or equiptment once you enter an arena. Today, me and my storm friend (I am also storm) went up against a team that stocked up on storm shields, and storm resist gear so that our attacks did nothing.
That actually happens? Don't worry about it too much. Unless the person you're against has a super high speed computer, they can't accomplish much, maybe changing a hat.
And, did you consider the possibility that they were already like that to begin with? Storm shields are usually in good player's decks to defend against Storm's crazy power with Waterworks gear. And Storm resist could still happen, though it's a bit less likely ...
