I'll work on the durations and able Blooded fix in two shakes of a lamb's tail - restricting Able Blooded to 'Abilities garnered in this manner are reduced in power to at least one rank below Nevin' s own, and can only be used on abilities up to one/two levels above his own."

But the thing about the special grade potions is on purpose - they normally would only be able to be used on an item, as trying to drink an Ability potion would conflict with the drinker when they're in a combat situation. Able Blooded is what allows Nevin to drink that level of potion in a combat thread.