Also, you know, it's pretty unfair of the game to present you with a bullet point list at your bed roll, for 'who do you want to pick' and you might have four or even five options.... and yet there's no "Invite both X and Y" option anywhere... This is supposed to be a party, after all...
(Note: said at least partially in jest; I absolutely do want poly conversation options eventually, somewhere in the game, but I agree that the way it's handled right now is pretty tacky and forced in the everyone-at-once-right-now set up)
I think it would depend on the character.
Dragon Age 2 had a poly/open sex scene with one of the companions where they invited a companion from the previous game who was very... open with their sexuality, but it made absolute sense for those characters to be in that scene. I would not want to see the fallout that would be inviting Shadowheart AND Laezel to bed... Though weirdly, I feel like Gale and Astarion could actually get along, but I have no evidence to back that up...