Categorizing items to fit champions
Make the items exclusive to champion groups so that champions wont need so much overall tweaking.
Separate items and champions into light, medium, and heavy categories. This way items and champions have a context and role. Then when balance passes are made less testing is needed on items affecting champions in unexpected ways. This does mean however that more items will need to be added; as the current items don't allow much room for diversity. The analytical nerds have done their homework and have concluded there are only particular itemization paths to choose from for each champion, and they are right... This can get boring fast when you build the same build (1 offensive/ 1 defensive item alternative).
Ex: building a medium category tank:
I decided that i didn't want to be a full tank because i wanted additional mobility and tenacity. If i chose hecarim 
over scion
as my tank, i wouldn't be able to select from heavy items like a randuins omen
or spirit visage
. but i could pick up a thornmail
...something along these lines.