IIUC, you're looking for candidates for semantic faces. In that case, I
imagine that it would be helpful to gather a dozen or so popular themes,
strip them down to the face-setting code, condense the specific settings
down into categories, and then synthesize the lists into solid candidates.

This seems like the sort of effort that could be distributed. I would be
willing to help out, but I don't personally use any of the more complex
completion frameworks, so I might have a big blind spot for the search.

Let me know,
~Chad