YAYYY OVERWATCH! I'll probably never get to play with you because our schedules won't line up. ;( Unless you come around on the weekend!) OKAY, PLOT.
Isabela - since she's Circle Bethany/Wear she's also my Hawke's! She's a snarky dual weapon rogue so they have that in common. She would've been good to Isabela so bffs please. XD Also Desmond here will like her (he's a cynical assassin) and I'll definitely throw Ezio at her again. I've got 3, canon, female, and teenager so they'll all be interested in talking to her.
Frank - Desmond might also get along with Frank for the same reasons. Teenage McCree has more flexible morals than adult. I'll probably poke Frank with him. Shepard too, even though his morals are less flexible, he tends to get along with most people.
Sarah - Portamis are modernized spies here so they should get along as well as they always do! Desmond has a son he doesn't know about yet who's and 11 year old Sage (he'll have intense visions when he's older), they'll probably get along.
Abbie - Porthos will LOVE her. So will both of my McCrees. I'll probably throw a whole bunch of people at her honestly.
Dela - I really enjoyed Ezio's friendship with her at Jaha so I'd like to get that back eventually. I also have Ezia and teen Ezio who will like her. Basically all my assassins. Oh and Ana is a field medic so they would've crossed paths. (Did you mean something other than ~waterfall? It's a blank journal with the name Lily.)