RPG romances have been quite controversial since Bioware decided all their games need 5+ of them (8 in DA:I!). I think RPG romance is fine in general, but when there's a bunch of them in a game, inevitably their quality and significance declines. A couple detailed, interesting progressions of a relationship are far more impactful than 8 shallow "press A enough times for sex" companions.
Not 100% sure what you mean by "romance based on character traits." You mean, like, if you're selfish, heartless, independent,, etc. you'll lose out on a chance for a romance with someone looking for a loving person (more generally, you need to have, say, 6/10 of the appropriate, compatible traits for the romance to be possible)? I think that's okay, but good dialog is the number one way to make a good romance.
I actually think there's nothing wrong with tieing some kind of gameplay effect to romance, but it should be a pro/con kind of thing. Like, say you gain some kind of bonus when you're in sight of your loved one (if it's a companion), but a minor debuff whenever you see them take damage. Nothing significant, but enough to convey a sense of love. And if you damage them too many times with AoE attacks or what have you, the relationship ends.
On an unrelated note, is the game ideas section on the uservoice site gone? Guess they just want pledge rewards.
