I'd love to see sub!Sherlock's first scene with John and Mary as his Doms. They're starting off slow, but something happens that triggers a memory from the years Sherlock was away and he has to safeword out. Cue aftercare from the finest Doms Sherlock could have hoped for.

Bonus: an exhausted Sherlock explaining why he was triggered and refusing to meet John or Mary's eyes.
Bonus the second: It's the first time Sherlock has subbed since he left London, and it goes really well until he's triggered.

Prefer no scat or watersports, but anything else is fair game.