I think Will could be another Hughie Campbell, another Billy Butcher. On his wedding day, his fiancée is a casualty when Homelander, A-Train and Queen Maeve stop a runaway train, and take out a bridge in the process. Natalie was getting her bridal portraits done nearby. It's incredibly tragic, and probably really heavyhanded. Will is, of course, offered a substantial sum from Vought to compensate him for his loss, and to...you know, maybe ensure he doesn't talk to too many people about that girl he was gonna marry. Will refuses the offer, is recruited by Butcher, and goes underground on a mission to use his medical skills to help the regular-ass humans trying to fight the super-abled.

Watts in Sherlock, I think, is a DI with the Metropolitan Police, and while some of his peers don't especially love Holmes and Watson getting ahead of them on cases, Watts is an admirer (in a very clinical sense.) He likes to compare notes professionally when given the opportunity, and isn't defensive of his crime scenes or snarky the way Lestrade can be -- he finds Holmes' methodology interesting, and treats him like a colleague.

And over in the MCU, I think we again are gonna cast him as a sympathetic member of law enforcement, similar to Jim Paxton without the familial angle. He recognizes Scott when he's arrested again at Pym's house, he's disappointed to see him burglarizing another home, but ultimately makes a call to help out Our Heroes using his police resources when he's called upon in their hour of need.

Also, his hat gets hit with a Pym disc and ends up taking out a street lamp.