I don't use any game engines, but my understanding is that CC uses ARKit facial blendshapes, not bones, so I don't quite know how your request could be granted.
As you mention, you do your own, so there are probably thousands of ways to do it depending on the developer. It would be hard for RL to maintain a generic version that would fit all those scenarios.
RL received a grant from Unreal to develop the interface to Unreal. For Unity, it has been made open-source and given to third-party developers, so that might be a feasible way to go.