I would have to go with no just because I want to stay on the side of safety. If it gets added, there is no going back. Also, if one of the mane six gets a romantic partner, I feel their status as a character goes up above the others. It is sort of the fear that Twilight would become more important than the others. It didn't happen, but everyone was afraid it would happen. So just to spare everyones emotions, I think it would be wise not to. Plus, haters, cloppers (not that I have anything against individual people), non bronies, and more would have a field day with the concept.