Considering the focus on making every single companions "attractive" romance options, I rate the chance of a small race companion very low. Halsin easily could have been an old halfling but Larian and its audience are more interested in buff and young half elves.
Well, I hope it's not true that the writers are compromising the companion selection for the sake of romanceability. Which would be, in my view, both creatively disappointing and almost certainly futile, as if characters are well written and engaging then players will want to romance them regardless. I say again ... Garrus.
But, even if that is happening, I don't know why shorter races shouldn't be considered attractive romance options by more than enough players. And while of course love should not be limited by size, my gnome, halfling and dwarf PCs in particular tend not to be naturally drawn to all these galumphing giants and would be more tempted by potential love interests of a proper size.