I think a Steve - Daphne coupling would be a better fit. Their characters would balance each other out and maybe even be a turn on for them.
Ok, characters we should be able to set up Steve with because he's a Bro:
Emily, we already had a muppets threesome together with her and him, wouldn't be that weirder, and who better to trust with our mom than him.
Sam, specifically if we date Stephanie. Maybe even get a foursome.
Daphne as you mentioned, since he's her viewer and it would be kinda funny.
Hot Mai, to "pair the spares" more than anything, then again I do think Steve would treat Ugly Mai right too, they could even gush together over how cool the MC is.
I was going to say Lexxx but with Good Melvin not being a incel piece of shit who thinks women are property I don't mind him getting Lexxx anymore, then again Steve could get his own Sexbot from Mai (Come on, it's OBVIOUS Mai was the one who built Lexxx and Alexa, especially after that sneaky little retcon).... Cirixxx? You know, Siri, Ciri from Witcher, etc etc?
Steve is turned into a girl by Alexa's box and becomes part of the Harem. She's still on the "heavy" side to appease to the BBW fetish demographic.
Steve doesn't get anyone we know of but gets the "Kevin from Power Vacuum golden ending," IE he gets an amazon scholarship and starts working out and becomes a high exec at Amazon HQ and later CEO, except since he's not a piece of shit he let's the workers unionise pays them more than a living wage and starts helping the world with Amazon's technologies rather than suck it dry for resources.
