Well, I have no experience with competition BBQ (yet) but as long as the dessert doesn't have to be presented in individual portions, a trifle would be easy to prepare onsite with limited cooking equipment and looks pretty too. Not to insult anyone's dessert intelligence, but a trifle is basically cubes of cake layered with custard, whipped cream, sometimes fruit==let your imagination go crazy== in a clear glass pedistal bowl. I do one for the holidays with gingerbread sprinkled with Capt Morgan, pumpkin custard, whipped cream and garnished with crumbled gingersnap cookies. Is this kind of thing on the right track?