Nerdy Men of Letters Dean AU, while we are playing the head canon game.
A fix it universe where Henry Winchester survived. He returned to his time and saved the Men of Letters.
He is over overprotective of his son John who rebelled by running off to join the armed forces for the Vietnam war. (Henry is concerned about the timeline forcing things.) Soon John returns disturbed by the war and needing the tranquility of the Bunker. He is frustrated but not able to think of something better to do with his life. Till a family of hunters, the Campbells stop by to get advice from the MoL and bam he meets Mary.
Henry is immediately torn. On one hand he knows bad things could happen(because again the original timeline seems to be trying to reassert itself). On the other, this is a chance his grandsons could still exist and he’s felt guilty for changing the timeline for just that reason. So he cautiously grants his blessing, relieved when Mary declares she doesn’t want to raise boys in the life and gives up hunting so she and John can live normal lives.
Despite his best efforts history tries to repeat itself and Mary dies and John flies of the handle and into hunting. Refusing to let his grandsons suffer the same life they had before, Henry demands custody of them while John is out and raises them both as good little nerdy Men of Letters Acolytes. Sammy prefers making a difference in the real world and still goes to College but Dean happily dorks out in the bunker determined as always to make one of his adult male parental figures (grandpa Henry) proud of him. Plus he has a best friend fellow initiate Charlie. (Henry made a lot of good changes to the men of Letters including gender inclusion.). Plus under grandpa Henry he’s allowed to explore being bi with another initiate without the fear of censorship he’d get from his dad.
However when he officially passes his last initiation right into a full Man of Letters and his dad doesn’t show up as promised, Dean starts to worry. He wants to go after him but he has no training in combat just Lore and magic. So he uses his new authority as a member to go into the restricted libraries the Men of Letters to learn if there’s combat magic or artifacts to aid him and stumbles on the lore they’ve amassed on celestial beings and learns about angels. Remembering his mom’s stories about angels watching over us, he summons and binds a guardian angel to him for his journey into the real world to find his dad. And Castiel answers.
And their first stop is to check in Sammy to see if he’s heard from their dad. And we catapult into a weird mirror of Season 1 only better with nerdy(and slightly clumsy and bashful and crushing on his bound guardian angel) dean, tag-along-Cas, and Charlie sneaking out armed with an arsenal of MoL artifacts she and Dean can play with.