The current plan (though we will take suggestions) is that Sage Mode will increase Slot values of other Slots for X Duration. So for example Sage In Training may increase 2 Slots by 1 PP (Max Grade 3 (Upgrade II)) for D3+1 Rounds.
While Perfect Sage will do something like increase 5 Slots to Grade 4(Upgrade III for you heathens) for D4+2 Rounds.
Gates, we started and stopped as the request for them was withdrawn. But they will be balance as Jutsu (specifically Kinjutsu+++).
