Adding amp-youtube to amp-story-grid

[TheRook]

I can see that amp-youtube isn't allowed, so it must be more difficult than simply adding it to the dependents list:
https://github.com/ampproject/amphtml/blob/main/extensions/amp-story/validator-amp-story.protoascii#L749-L750

What is involved in fixing this roadblock? I feel like amp stories would benefit greatly from allowing amp-youtube, seeing as amp-twitter and amp-video is already being used there should be a way for the community to fix this issue.

What is involved in fixing this short coming of amp-stories?