The "For the Enclave" mod available via NexusMods allows players to join a splinter group of the original Enclave as it goes head-to-head against their former brothers-in-arms. The mod adds a five-part main quest, four side quests, new voice acting, a potential companion and even an Enclave radio station.
Rookies need not apply, though; players who want to undertake this mission must be level 15, must have interacted with the NPC Benny, and must be running the most current version of New Vegas on Steam. The mod's description text also warns that it will be incompatible with most mods that alter Searchlight Airfield.
Fallout: New Vegas (Lonesome Road DLC)