Probably a subcategory wouldn't be considered unless there were four or five sites ready to go into it.
So the trick is to suggest four or five sites, and then, in each suggestion, put in brackets "[suggest putting this in new category Blah-blah-blah]"
Some of the suggestions could be sites already listed in the parent category, in which case you'd do an "update listing" suggestion.
New categories are added "as needed", not "as suggested". So the time from suggestion till recognized need is, as always, unpredictable.
