Point and laugh if this is already available, but also please tell me where to find it.
How about an addon that makes use of the screen flashing overlay frame (many addons use it for low health or aggro but I don't know what it is called) whenever Player receives a buff/debuff on a custom list they create for themselves? As a rogue, I'd add lots of things I like to remove with Cloak of Shadows but sometimes miss in the heat of battle and end up wasting a heal or two on me. For general purposes, it could work for Solarian's updated Wrath of the Astromancer and similar abilities to let you know it's time to do something but not requiring you to stare at the debuff list so much.
Customization (if they're even possible):
- List of buffs/debuffs that make it go off
- Color (per buff/debuff maybe for fights with multiple effects to distinguish them)
- Number of flashes (probably not necessary to flash until the (de)buff is gone)