I'd say a final test in culinary school is all about the fundamentals, I dont think you should go out of the box on this one. When I attended there were a lot of students that were trying to run before they could walk. Your original idea of the meat, starch, veg and sauce is what I think you should stick with. Pulling off a perfectly cooked and seasoned piece of beef, buttery potatoes and crisp yet tender blanched veg with a spot-on béarnaise would impress and please anyone. The only recommendation if you go that route is to make sure there's a good balance of vinegar in the base of the sauce, you want to show you can cut through the rich flavors on the plate even though even the sauce itself is butter/egg based. Good luck!