I just watched the Romance community update. It seems that Larian do take a lot of care to implement romance as a narrative and cinematic feature.
They want players to care about the characters and impact that such relations have on the story.
But I want to suggest something that could take that impact to the next level - gameplay.
What if characters who are in love could gain a treat that would enable them to react to things that happen in the fight? Perhaps even automatically?
For example, Shadowheart could have a chance to cover the player with a shield from an attack, or the player character could immediately counterattack the monster who hurt their love interest. Rule-wise it could work based on the reaction rules similar to some spells to stay true to the DND source.
The closest I have seen to this was either the new unique skills in Tyranny, permanent buff to the stats in NWN:Mask of the Betrayer, or the friendship system in the XCOM series.
Of course, it may be seen as an imbalance, but imagine the impact such system could have on the player. We would spend 60 to 80% of our time in combat, and having romance change something about how characters behave in combat and not just in dialogue would be precious and previously unseen in RPGs.
What do you think?