I'd want a Harold/Player/Feliar purely because I think it would be a fun one to see since Feliar is all about going with the flow while Harold is kind repressed(even when he's open to sex and whatnot) so it would be fun seeing how it would go.
Another one I'd want is Barrel/Player/Andrey simply because of the endless amount of kinky content that can come out of it.
Also one I'd think would be interesting albeit completely unrealistic would be Torben/Player/Harold and it is just so we can see another side of Torben when Gunnar is not around(he needs more love he's just kind of there mainly like the only occasion where we can interact and have sex with him without Gunnar is at the fair)
There's also a Player/Scrap/Tao threesome for Dom top players and there's also a Torben/Player/Gunnar one at Torben's house.