I think it'd be fun to go back to New Vegas or the Capitol Wasteland then instead of the Courier and Lone Wanderer youd find a Brotherhood Controlled Wasteland and Yes Man controlled Mojave.

You'd meet Yes Man with his new more assertive personality(i cant be the only one who always wondered what he'd be like when he came back online) and he lets you in the Lucky 38 for the start of that DLC's Main quest in which Yes Man has detected NCR and The Legion(New Name of whats left of Caesars Legion) preparing to make a final push into the Mojave Wasteland(opposite sides of course) to take the Dam and The Vegas Strip and he has determined that the size of the two forces are to large even for the Mark III(Yes Mark 3 Yes Man/Courier found a drive to upgrade them) army and he needs a mind like the Couriers to help him and hes determined that you have the necessary skills to help him defeat the army.

While your scouting the NCR/Legions camp(whichever you chose to scout first) you become a captive of that group and you have choices to make- You can either Break free after the interrogation when your guard falls asleep(your items are all in a locked chest to the right of your cell and the key is on the sleeping sentries desk OR when your being interrogated you can tell the interrogator about Yes Mans plan and convince them a Temporary alliance with(depending on what camp you went to) NCR/The Legion(unlikely i know) would be the only way to defeat the securitrons and you can then tell them how the best way to defeat whats left of the Temporary Allies or you can convince both parties to split the Mojave and its MANY new settlements that sprout up since the Courier took Vegas and went out on multiple extermination/capture trips to destroy/capture the more dangerous breeds like the Deathclaws which would be exterminated and the eggs would be sent to farms to be raised as friendly Deathclaws for the eggs they would produce while creatures such as Cazadors would be exterminated and Nightstalkers were raised as house animals after exterminating the wild ones and there would be many new creatures thanks to the most dangerous predators being exterminated/tamed different species would thrive and mate with other species while new species would move in.(i know kinda got sidetracked there the main quest would have alot more to do then just what i posted)

While in the Capitol Wasteland you'd be taken straight to Sentinel Lyons(The Girl Father died while out on a patrol with some of the best paladins the brotherhood had got taken down by a hoard of what the lone survivor described as 'A bunch of fucked up raiders who kept yelling something about a thing called the "Punga"(yes the brainless creeps found their way here under new leadership by one known as Daughter Punga) and the Brotherhood has discovered that they managed to salvage what appears to be a mix of Enclave/Outcast/Brotherhood Power Armour(meaning that their leader must have spent time with one of these factions long enough to learn how to use this amour and then retreated to Point Lookout) and they need help keeping them from overwhelming the Wasteland.(I was tired and ran out of ideas after the Mojave one so i might add to this at a later date and yes i know the beginning of the Capitol Wasteland is the same as Mojave like i said i was tired and ran out of ideas)