Actually, shouldn't items have a priority of 7?
This is a minor nitpick, but there are priority 6 moves.
Ofc it wouldn't matter, since those are protect and such, and they'll fail if you use an item.
But still, the item should always come before Protect, so it should have a higher priority than any move (even if this is a theoretical issue more than anything).
Well, I don't know if Protect and Detect and such actually have the priority of 6 in Essentials... they're listed as such on Smogon, I believe.
Anyway, I'll have to reread the item issue. Reworking the whole class sounds rather daunting though.
(Couldn't you just use the item quantity as PP? Well, not good because then Pokémon centers would recharge your items. You might as well add som sort of "quantity" on the move class and use it exclusively for the items... I'll leave you to that; you have it way too developed in your head already x) )