I am not super interested in tattoos, body writing is absolutely a fun idea, and i'd love to see some nipple piercings on the girls maybe with a chain connecting, or like some little dangling crosses for Linda. But generally Body paint as clothes, transparent clothing, collars, leashes all sound fun.
I'd love to see maybe daily selfies from MC's girls as a way to check in. As for character specific things I think would be cool.
Jenna: MC walks her from a leash attached to her anal plug in public.
Linda: A scene where the MC stumbles on Linda baking and then after some typical interaction between the two covers her (face, and or shirt and boobs) in cum and then makes her send a selfie to her husband and or daughter showing her "baking mishap in the kitchen today" passing the cum off as batter or something.
Emma: we have to have a scene where the MC gets Emma to wear a mask* at the strip club and tricks her son to either unknowingly getting a lap dance or more from a masked Emma, and or watching the MC get a "very special" lap dance from a masked Emma without knowing maybe with the option to reveal it at the end.
Scarlett: more cucking her husband the more depraved the better, last scene was great, maybe have her text a pic of the "results" of every encounter to her husband and make him praise the MC on how much better of a job the MC does than the husband.
Kate: I mean Kate has happily accepted being so demeaned and depraved at this point I think the only place to go is to have her maybe make her submit to stray dogs for the MC's enjoyment.