Image generated with DeadmockI wanted to come up with an ability that encourages players to buy active items, without creating an incentive to only purchase low-cooldown active items. To this end, I thought that a passive that rewards players for having used their active items rather than simply giving temporary effects on use would be helpful.
In retrospect, perhaps this concept punishes players for holding their active items for the perfect moment. A way to address this would be to cap the number of stacks to three rather than four, so the player feels comfortable keeping at least one of their active items as an emergency tool.