The game is based on resource management and I think the main reason I would be looking at timers is to move SP to the point were we are beyond being able to replenish it faster than we use it. That's why it's not a true restriction on casting when casting is balanced based on that restriction.
What I'm getting at is moving back to a point where the rate SP can be recovered becomes a point to consider when SP dumping rather than simply deciding we want to have more SP as needed if we can just refill on a whim. If we can replenish faster than that we can dump faster than that for more effectiveness.
I think that if the game is balanced based on not using potions that can easily be out of balance with potions regardless. So far I haven't seen a very convincing argument as so to why it is good for the game.
I am convinced it's not widespread, high priority, and not sustainable. To me that doesn't actually change the game mechanics involved.