I would also like people to be able romance each other in multiplayer, regardless of whether they are playing a Tav or an origin.
But I have a feeling that would be hard to do, and even harder to do right. The dialogue function can be used between player-controlled characters in-game, at least, it could the last time i played multiplayer, which was during EA. What we're lacking is player-to-player approval, which is one of the main factors in how romance progresses with npcs. In order to start romance, there are checks on both approval rating and dialogue choices. If you throw out the need for approval, now it just becomes dialogue choices only, and there is a problem in that i feel like many people want different things out of their romance.
What do you want, specifically?
Do you want to play with your partner and just be able to trigger a romance flag that lets you use dialogue options to smooch your partner's character whenever you both want to? (I am always in favour of more smooches)
Do you want to initiate sex scenes with the other player? (they would have to agree to it, and it would be somewhat awkward with no voice acting, but it could work).
Or, do you want larian to write some kind of romantic progression plot for both players to follow which will eventually end up with the option to kiss and possibly a sex scene, like if you were romancing an origin character?