I find that when entering competitions, it is a better use of my money to enter anything that isn't a "normal style" only where there are people who are likely to judge it who have experience with the style from both a scoring perspective and for feedback. Smaller competitions probably won't have a wide enough range of judges to be able to judge Melomel well. If the judges are unfamiliar with the product (commercial examples, making it themselves, etc) prizes will be a crap shoot and feedback isn't likely to be helpful. But if you know a competition has an experienced judge pool or draws from a deeper pool of judges or even if the area specializes in something, I think you'll find the quality of off-centered beverage judging to be more satisfying. Part of that is that the competition organizers will know what the judges will want to know and how they might handle too much information on first taste.
Summarized, I would email the organizer of a competition with a question like this. If they don't have a satisfying answer, I'd skip it. It's more about getting a specialty product to the right judging panel. You wouldn't send a Big Rig to Car and Driver for a test drive...
or maybe you would...