I don't know about the romance part. Yes, maybe it seems cooler to say "A god loves me" than "Some elf loves me". I am not a Solasmancer, so this is an emotion that eludes me. But if I were I would not care what he is. Because I would not have known who he is (Lavellan: not at all, player: until the ending scene), so I would not have fallen for a god but simply for an interesting person.
It has nothing to do with him being a god or not. Personally, I see him as 'some elf' regardless of the outcome. I don't personally think that any of the elven gods were legitimately deities. I could be wrong, of course. I'm always willing to change my mind when additional lore finds its way to us. I'm just attempting to explain my mindset here.
There's two reasons why I tend to side against the idea that Solas is Solas+Fen'Harel.
The first reason is what I stated earlier. I think Solas's story is much more interesting when all of the mistakes he has made belong solely to him. There's no shared burden. He's a singular flawed character rather than two that became one. There's no easy out. There's no way to brush a sin underneath a rug. Every life taken, every error in judgement- it is all on him alone. He is dreaded. For all we know, maybe he's beyond redemption.
The second reason I'm not a fan of the idea is because it somewhat muddles the situation going on with Mythal and Flemeth. Mythal clawed through the ages to get to Flemeth. If this was something that all of the elven gods did, and was common knowledge- why use such strong wording? Why is Solas seemingly surprised to see her still alive? Why not emerge sooner?
It seems more likely he's just Fen'Harel, and Mythal is the unique case.
[As for the other part, about them not separating- I do agree. I was simply using that example because it is a common idea people have as a way to get a happy ending.]