AU where there are no human titans and everyone in the 104th was what they appeared to be at face value. Mikasa, Eren, Christa (and Ymir) join the Survey Corps, the rest of the top 10 join the MP as they originally intended.
Reiner, Bertholdt and Annie are all from a relatively poor village — Reiner and Bertl are thrilled to live in Sina and finally be able to afford haircuts and nice shirts (with things like collars and buttons!). Reiner is charming and a natural leader, and makes captain within several years.
Annie never spends any of her military stipend — she saves all of her money to try and earn enough to move her father out of poverty and inside Wall Sina with her. She has all the people skills of poison sumac, so she can’t manage to get promoted at all. But higher ranks come with larger pensions, so in desperation she turns to Captain Reiner to teach her how to interact with other human beings.
Reiner is so thrilled. He knows about popular, Annie.
(Annie’s fancy embroidered shirt was a gift from her hometown comrades Reiner and Bertl after her hooded shirts started to get seriously manky and gross from years of continual wear and crappy patch jobs. They had trouble conceiving of clothing for someone as tiny as Annie, so the shirt they bought is still too big even after Annie took it in by hand. Reiner didn’t know she wore DOLL CLOTHES OKAY, HE TRIED.)