As usual flexibility of the dialogues, that is more options and a more smooth progression, would be the best.
Also due to the fact that herosexuality litteraly makes able to players of any gender identity and sexuality to try to have sex, romance involves sex but its different from sex for its own sake, with any choosen character, I don't get why the asexual option (as much as asexuality could be a lesser fraction of sexuality), is not considered.
In other words Larian talks about "romance" while in reality is only sex, beware I'm not saying there's something bad in this kind of sex. Litteraly the dialogues that imply flirting are few and some difficult (if you are a bit naive about flirting, like I am, seriously if someone is not explicit with me I don't understand if thei are flirting

) to understand.
Maybe they could add the flag [flirt] just like they have those for race/class/profiency specific answers. I dare to say two different flags [romance] for those who prefer the romantic side, [flirt] for those who instead want the physical aspect too.
Obviously they should modify the attitude toward the main toon system in a way that it follows five different outcomes:
1) (low or no approval) and (no flirt or romance): the companions in this situation are cold borderline hostile with their answers, thay could too sush away the main character;
2) (low or no approval) and (flirt): the companion could decide they despise you but still hot enough to bed them;
3) (high approval) and (no flirt nor romance): the companion is friendly, they are open and share with your main toon, they show their trust, but they don offer to have sex with your main character;
4) (high approval) and (high flirting no or low romance): the companion appreciates your character but sees their relationship like one of "friend with benefits";
5) (high approval) and (high or low flirting and high romance): the dialogues let the player decide if go into a romantic relationship, a "friend with benefits" one, or a romantic and sexual one.
I put the approval as first value because making the exception, of the "well they're hot so what the hell in the end is just sex" option, a low approval means that the companion is not availabe.
I know that manage three different factors is more complex but that way would gave more flexibility and chances to have a personalized playgame with different outcomes that are not tied only to the fact that the companions get attracted by you not because off how you flirt or court them but because you make some story related choices that align with their own view of the world.