Yeah it has to be playable. You can come up with your own objectives if you have some ideas. Otherwise just a standard fight with some weapons. Weapons could start nearby rather than in the hand, so you have a choice of what one to use. Try to give it some gamerules to suit the type of fight, not necessarily sparring settings though i.e. enough gravity to walk around, and turn frames not so long that you can't do precise moves with the weapons, and turnframes not too short that the game takes a long time.