You don't always have to wander the wastelands as a grizzled survivor of a post-apocalyptic hellscape. Sometimes you can play as a smartly dressed, time-travelling British gentleman instead.
First things first: this isn't a mod. It's a guide to role-playing Fallout: New Vegas as a character (and player) matching the Doctor, so aside from advice on picking up a suit and glasses ASAP, this is about stats and playstyle, not a texture swap.
But it's a pretty cool guide. Basically you're picking your stats to best reflect the approach the Doctor would take when confronted with New Vegas. This means lots of talking and no killing: get through to the end of the game with these stats and you'll be able to talk your way to the credits.
You are now equipped to lockpick, charm, and hack your way to getting to 100 speech, 100 science, 100 lockpick, and 100 medicine. You'll have to let Benny betray you and run away with the chip, but you can sprint past the army of death robots awaiting you beneath Caesar's camp (indeed, this is my favourite part of the game if you've got I Am The Doctor blaring out of your speakers).
You can, and will, defeat the endboss through conversation.
UPDATE: Of course there's a mod as well. Of course.