It’s going to be really situational and depend on how much you want to put in. If you’re ready to tackle a complex relationship dynamic, I think you can—especially as you’re taking the work to get input on it—but there’d also be nothing wrong with deciding it’s more complexity than you want to handle. It certainly is something that would require plenty of sensitivity.
Right, so that’s just wrong. That should be especially clear with the aesthetic side because, well, I can’t count the number of people whom I’ve felt look nice but I don’t feel physically drawn toward. But people can feel sexual and romantic attraction in different ways. The genders preferences for those don’t have to match. There’s also the notable difference between “primary” and “secondary” attraction, which can come into play for demisexual or demiromantic orientations, secondary attraction being attraction that you only feel after emotional bonding. Some people are attracted to people of one gender right away but only feel drawn toward another gender after forming such a relationship. Sexuality and romance can be a lot more complicated than the typical labels, and the two don’t always coincide.
That said, for a lot of people, romantic and sexual attraction are very connected. Some gay people have felt backlash against split attraction models because they consider it to deny gay sexuality as a component of gay romance. I can see this being valid and important for certain people; there are people for whom these types of attraction are indeed inseparable. But that shouldn’t invalidate people for whom they are separate.
Like, as for myself, I definitely seem to be just gay on the sexual side, not quite sure on the romantic side (very into guys, had female crushes as preteen/early teen, not sure I’ve felt that since then), and aesthetically I’m very much on the feeling that, you know, lots of people are pretty 
But even if we restrict ourselves to men, I’ve definitely experienced romantic and sexual attraction feeling different and not always coinciding… They’re not always completely the same thing.
Well, you can also just be explicit about having the character present himself as panromantic homosexual. At least at some point before the romance happens. That’ll help present it as something that’s just true about him rather than something that’s just there for the player’s convenience. It’d depend on what conversations make sense in the context of the story, but really, the more explicit the better.
If it’s already clear, pre-romance, that he likes women but not sexually, it won’t feel like it’s forcing anything.
That also sounds to me like something that’d make a big difference. Hardly a heteronormative result.
Does it end up as a V or a triad, or possibility of either? What’s the boyfriend’s orientation?