Okay, here's the score:
Currently, you can set any item to increment any of the various counters on item pickup.
You CANNOT--however--tell an item to deplete a counter when it is used. The only options for counter depletion are the MAGIC counter and the RUPEE counter, and these are controlled with flags.
I propose that we replace those two flags with a pulldown just like the pickup counter modifier. This would eliminate a lot of redundant scripts and enable easy use of some of the more popular features, like items that use different types of ammunition. It would even make the True Arrows rule redundant, as we could just directly set the arrow counter to be depleted by bow items.
Food for thought.