This is another way to play that requires player trust but isn't too complicated.
I would say this mode should be about as simple and easy to understand as All Random All Middle.
LoL RAW plays like a normal match in either Summoners Rift or Twisted Treeline.
The main difference is that no one on either team can purchase items at all. Not even wards or potions. This is a mode that challenges you to see how well you do with your champs base stats, your runes and masteries, and your chosen summoner spells.
(This is still experimantal so wards and potions may be allowed if everyone agrees to it. This makes things interesting considering the last rule.)
Because a game like this would probably last quite awile I think this last rule will help wrap things up.
FINAL HOUR: Final Hour occures when every member on both teams has reached level 18.
When this happens, the previous rules are tossed. All items can be bought and the game intenses. Suddenly all that gold that was sitting in your bank turns to four big items or so and the game can quickly draw to a close.
This causes you to both farm for experience and to save up as much gold as you can during the main part of the game. I think this should make for an interesting match.
I will admit, this is another mode thats going to be easier for LvL 30's than anyone else but not much can be done about that.