Awesome! That's one of the best natures you can get! Here is data for uxie to hold leftovers:
~ Yawn
~ Stealth Rock
~ U-turn
~ Thunderbolt / Grass Knot / Protect
252 HP / 252 Def / 4 SpA
This set is all about softening up your opponent and setting up the rest of your team for an eventual sweep. Bring Uxie in on any one of the multitudes of Pokémon that are unable to do appreciable damage to it thanks to its colossal Defense, and use Yawn or Stealth Rock. Your opponent will probably switch to something like Heracross that will force Uxie to flee, but that is just fine. With such great tanking stats, Uxie will be able to switch in repeatedly without difficulty, allowing you to rinse and repeat the Yawn/Stealth Rock process until you have both slept a Pokémon and Stealth Rock is out on the field. At this point, when you bring Uxie out, you can just start using U-turn while your opponent goes to their counter, choosing the appropriate Pokémon each time. Obviously, this set will force a ton a switches, so it works best in concert with Spikes.
The choice of the fourth move depends entirely on what holes need to be covered in your team. Thunderbolt gives Uxie a leg up on Gyarados and Starmie. However, Grass Knot knocks Rhyperior on its behind (Tyranitar is only 4HKOed) while Protect lets you scout Choice Band users, gives you a free pass on the turn Yawn activates, and gives additional Leftovers recovery. Psychic receives STAB and hits Heracross and Infernape, but Psychic attacks are in general liabilities in D/P, and Uxie should try to U-turn out of what Psychic hits anyways.