Have you seen the actual rules for the anything but category? Sometimes the organizers are way less restrictive with the rules, such as allowing different garnishes or allowing cheese, bread or even toothpicks to hold your creation together.
One of the best anything but boxes that featured beef that I've judged was nachos. But not the pile of chips with a gloppy topping.... individual ones. I'm almost positive they (coarse) ground some beef tenderloin, and they used a cookie cutter to down size tortillas so 6 nachos fit into the box. They had sort of an enchilada sauce on the bottom, then the seasoned beef, then a pico de gallo style of salsa, and a dab of Mexi Crema on top. Being mindful of the fact some judges don't like spicy food, the sauce and the pico were flavorful, just not hot. The pico had a nice crunch for texture.