Being able to visualize the progress of a buff stacking to X would be sweet.

As an example, shadow priests can choose the talent Idol of Yogg-Saron, which summons a Thing from Beyond upon reaching 25 stacks. A special type of bar that lets you choose to track a buff and specify at with how many stacks it reaches 100% would allow you to visualize the progress towards triggering the summon.

Observations/complications:

• There's a large number of use cases for various trinkets/abilities.
• Could probably be used to emulate resource bars as well, since that data is usually available in the form of a player buff.
• This would likely require a new type of bar, similar to how conditions are part of the "notify" group of bars.