I'm sorry, but that sounds like fluff and decoration, not actual gameplay content.
Because player romances aren't fluff and decoration?
What gameplay content do they provide? A low effort sex scene? The ability to initiate an awkward kiss scene?
Meanwhile, I suggested things that could actually impact gameplay (Rivalries that make certain companion set ups not possible)
You literally ask us to passively view someone elses romance.
A mere "by the way, we two are together now" would suffice for me in that scenario.
I mean, it's up to you if you want to sit there and expressly watch their romance progress.
Beyond that, there might be some dialogue changes in the likes of expressing concern if someone is being put into a dangerous situation (Including stuff like the altered barks that happen in BG3 when a character goes down when the player has high affection), some subtle changes like their tents in camp moving to be together.
Nothing that necessitates detracting from the general gameplay, but that still provides a nod to the fact that companions are in fact, people who do people things like form connections (With entities outside of the player).
Which would also highlight the fact that IF the player successfully initiates a romance with them, it's because the player managed to grow close enough to them in order for it to happen. Rather than BG3 where it's just assumed that every companion will automatically be lusting for the PC and no-one but the PC (Despite Wyll's, terrible, attempts to woo Lae'zel and Shadowheart in dialogues when roaming around together in a party)
