I think this one is good organicdirectory-thecatname-1, number is fine
with me, even it is not necessary. When I was making a new blog I
always used the dash sign. I just like putting it instead of slash.
The only way I can think of the top of my head to lose the number is to make the folder name a reference in the DB.
So you would have /my-directory/ stored in the categories table and then use a rewrite rule to use the my-directory part as a look up for the category ID.