Thank you guys.
I decided to leave as is.
still trying to figure out how sub-tags works.
I'd like to have lots of locations as secondary-tags (US states, popular cities around the world - London, Paris, Berlin, etc).
Let's say I have:
Primary - Construction
Sub-Primary - Carpenter
Secondary - Location
so the user will chose Construction, Carpenter then location. Locations will be under "Carpenter".
whats the best to do it?
secondary tags (locations) will NOT be visible on widgets (sidebar).