Mark, that’s extremely comprehensive and I love it! Like you said, it would help readers avoid things they don’t want to read in favor of those they do.
Interestingly enough, I think speculative fiction has gotten pretty good about breaking down their categories. Just think of all the “punks” there are: steampunk, cyberpunk, dieselpunk, solarpunk/hopepunk, retropunk, biopunk, etc. Not to mention alternative history, time travel, slipstream, first contact, artificial intelligence, clones, and whatever else you can think of.
On the surface, it seems overwhelming, but I think romance publishers could take note and whittle down their categories as you have done. I don’t think it’s unreasonable to say that any niche in romance, no matter how small, will find an appreciative audience.