The only thing close to this I've ever used is allowing multiple tags on the same aspect in certain situations.
For example, a thief-type character pulls off a big heist. I might give him a "Loaded with Cash" aspect. "But," he says, "That's only gonna give me a +2 on a single Resources roll! Surely I stole more than that." So, I tell him that he has three free tags on that aspect instead of just one, and we keep track of how many times it's been used. When all the tags are used up, the aspect goes away (or, in the case of the Volcano, starts costing fate points).
This works well when players have earned free tags (due to an awesome maneuver of +6 or more, or pulling off a scheme of some sort), but what to do when you just happen to be near a volcano, and no player has free tags? Well, you could allow them to invoke the Volcano aspect twice on the same roll, but it should still cost them two fate points.
The problem is, as soon as you let a Fate Point have more or less value depending on what aspect it's invoking, you open up a whole new metagame ripe for abuse and imbalance. Why would anyone ever spend a Fate Point on an aspect that only grants +1 or +2, when they can search around for a juicy +3 and only tag that. It also encourages players to make their aspects from maneuvers and declarations as outlandish and impressive as possible, in hopes of getting a better tag, even if the aspect doesn't totally make sense within the scene.