Larian has said they want the relationships in the game to feel like you're dealing with real people. And I'm not talking exclusively about the development of romances, but the development of the character relationships as a whole. One of the most common complaints I've seen on these forums regarding the characters is the jarring suddenness of the romance opportunities at the camp celebration and I think this speaks to a need for more individual character moments that help define the type of relationship the pc will have with the NPC.
Approval systems are not inherently bad--Dragon Age Inquisition used theirs in such a way that I often forgot it existed which was *perfect* execution. Approval should act as a tracker only for triggering relationship milestones. That is, important moments that thereafter change how the npc treats you, be that as a friend, a rival, or a potential romance. An example of how this could work is an early interaction with Astarion. If you've treated him with understanding after his vampiric revelations, he should thereafter greet you as a friend. Alternatively, if you treated him like a monster, his attitude toward you should be more negative. Furthermore, if flirt options were added to these relationship milestones, an NPC could be flagged as a viable romance option for the pc. This last point is the most important, since some players may want to try romancing everybody while other players may not want to be bothered with it at all.