[Characters] Allow characters in a category to filter down into sub-categories

eFiction 5.0 is great news!

The best way to describe a feature I'd like you to consider is to illustrate with an example, which I hope is clearer than the last time I asked about this possible feature as it was sadly misunderstood.

I have a multi-fandom Fiction archive that has a category for The Magnificent Seven. The fandom has a number of Alternate Universes, which I have made as sub-categories as it makes it easier for the reader to find what they want instantly without having to go to the advanced search. The problem is that I want to put the list of main characters in the top level category ONLY (The Magnificent Seven) and have them filter down into the lower level sub-categories automatically.

At the moment, I have a choice of:

1.  setting each character up ONCE in the top level category (The Magnificent Seven) and then having to assign the story to BOTH that category AND to the sub-category
Disadvantage: the story is now listed under both top and sub category rather than just under the sub-category

Or

2. setting each character up in both top category AND in each of the 15 sub-categories.
Disadvantage: impossible to search for all stories with a particular character as the identical character name is now listed in the search under 16 different char ids.

At the moment, my way around it is to use a combination of option 1, and then when I have free time, going into pHpAdmin to manually add the charid to the story and remove the higher level category. It's obviously not idea and only works as I have a VERY small archive with low volume of traffic.

My thoughts:

table character
col1: charid (system generated unique key)
col2: character name
col3: description

table character-category
col1: charid
col2: catid

eg:
table character: 99, 'Chris Larabee', 'Leader of the Seven'
table character-category row 1: 99, 124
table character-category row 1: 99, 125
table character-category row 1: 99, 137
table character-category row 1: 99, 138

This way a single character can be assigned to multiple categories, and the admin could even be given the option when setting up a sub-category as to which character(s) can be filtered down from the top level.