If they ever do a BBS2, Beast's Castle definitely belongs there. I think there's a lot in its past that could be shown. I'm thinking Gaston would have drawn the Heartless himself, but if not, Maleficent obviously brought them there because the Beast followed Belle after she was kidnapped to Hollow Bastion. Obviously, Gaston must've died in some way other than the way he does in the film, otherwise the Beast would've also died--cue Belle's tears, and then he would've already been human.
If not, I can definitely see them having Beast be cursed again in KH3, likely by Maleficent, another sorceress--and she did know him at Hollow Bastion, so it wouldn't be such a stretch that she would curse him if she met him again.
I guess when you say it that way it does seem possible. I'd love that in BBS V2.