Romances are already optional. I just disagree with notion of devaluing them by making the sex within them optional as well and hence offlimits for dialogue or the romance narrative.
How does optional sex within a romance devalue said romance? As far as I am aware, romance tend to be defined as an emotional attachment, not a sexual attachment. The optional sexual content or lack of sexual content would not prevent romantic dialogue nor a romantic narrative. It would merely omit the sexual scene in a way perhaps similar to a fade-out or keep it ambigous as per the player's decision should it be optional.
To some, an optional interpretation of a relationship can serve to avoid some very unfortunate implications such as with the Solas romance in which it could have become a question of questionable consent considering he is deliberately withholding information about his true identity from the player and masquerading by a different persona because he knows who he is will likely prompt a negative reaction from the player especially given his goals as well as his involvement with the plot.
I love the Solas romance and I am glad for the ambigous interpretation because it allows the romance to exist without Solas' character having be impacted in a bad way, in my opinion, by having to abide by the previous rules of an obligatory love scene.
TL:DR: Not adhering to obligatory rules in regards to how a relationship narrative has to play out can allow for interesting romances that might not otherwise be possible due to how damaging they could be to the characterization of the romantic partner if said obligatory rules were adhered to. Additionally and importantly, romance tend to be defined not as a sexual attachment but as an emotional attachment therefore it would doubtful, in my opinion, that romance would be made less significant per an optional lack of sexual content and less romantic.