Going out on a limb here but I was looking to see if I could find a Mycroft Holmes or Greg Lestrade from BBC Sherlock. I have a few ideas that I am looking at but willing to discuss if you have anything you want to do.
*Warnings for ABO and MPreg*
First one is a steampunk like setting. Not sure what will happen just looking into it.
Second one is an ABO plot where either one of them is an omega that has been hiding as beta and then a new law goes out and they can't find suppressants. Maybe they are friends before hand. Maybe one goes into heat before they can get to a safe room and the other saves them and fun smexy times ensues.
Next idea goes off the first but Greg is the omega and he was never able to have kids with his exwife so he left him. Greg feels worthless until Mycroft offers to help him through a heat and surprise surprise babies happen.
Last idea is cannon up to when Sherlock comes back after the fall. It brought Mycroft and Greg together. All was right in the world until Mycroft decides that he needs to end the relationship before he gets too invested, spoiler alert he already is. Later Sherlock comes back and now Greg and Mycroft have to see each other off and on. Greg is hurt and does not want to let Mycroft back in and Mycroft realized he made a huge mistake.
I am also interest in a BDSM spin of these two. To tell the truth I just want these two.