I remember Gaider mentioning a lock down on a no Cole romance thing somewhere as well. But... where it was is hard to point out. Someone mentioned before how they thought Gaider was being a butt about it yet I remember it being very reasonable why he didn't want Cole romancable.
Cole does fit the rather prettier boy of the party slot other then Cullen, but Cole is much younger. Him being interesting as a LI purely by his looks, or for the 'repair the damaged' type. If he does end up being one, I can imagine it being a veeery long and difficult process to even get him to do a little cheek kiss and never doing a physical romance until he becomes more comfortable and trusting of the world around him. And I mean, totally not just shoving gifts in his face till he's sparkly happy, which I know Bio had said they are no longer doing and are doing a new way to LI, but I would still figure a friendship is what Cole needs. Romance is complicated and carries a lot of rather strict things to it, which would probably be complicated and stressful for him since he's never had one before and his understanding on it is vague. He just needs people there who can see and remember him, to talk to him, things of that nature. Romance is sort of like friendship, but generally so far in the DA games it always is something physical rather then a platonic love, and since Cole had a very platonic level of friendship with Rhys that's as far as I can see Cole ever going, and that was some powerful love without a single move of the romances we see in game.
A hug, him sitting next to you, quickly running to your side automatically if hurt, a conversation, a smile. That's the sort of things a 'romance' I would prefer and figure they would do with Cole and hope they would if he does end up as one.