Without beating around the bush too much:
black_legwear -pantyhose -thighhighs -kneehighs -socks -leggings: 17879 posts.
We have comparable numbers for all the other implications. In retrospect, I think it was a pretty bad idea to alias these rather than just periodically move them (which could be easily done with a script). Having these aliases causes a massive loss of information.
Another example:
eyewear_on_head -glasses -sunglasses -monocle: 1654 posts.
People just don't care or don't notice about them being aliases, they'll just continue using "black pantyhose" etc because it's easier, without thinking that "pantyhose" will never be added as a tag. Any benefit that these aliases might bring results in a continuous loss of information that does more damage than benefits. The original idea was to for example search for socks black_legwear for black socks, but what if nobody is adding the socks tag?
Just for comparison, black_legwear socks returns less than 17k posts. That's less than the results under black_legwear -pantyhose -thighhighs -kneehighs -socks -leggings.
Are there any good reasons to keep these aliases rather than just having them as do not use tags and periodically sort posts in each tag? We either do that, or have to sort through tens of thousands of posts for each variant inspecting every single picture manually to see what tag is missing.