Can you adopt the system that this other addon here uses https://wow.curseforge.com/projects/mutilate which has a smooth colorful dynamic global cooldown 'spark' on the suggested icon even when the ability is off global cooldown that makes it slow down accordingly when it has no energy available to use the suggested ability so it kinda predicts when you will have enough energy making it amazing in my view! No more need of grey/fade out icons, I think this is the way to go, and perhaps it can also work with the 'pool' icon as well.

Do you have an example/video ?

Well I found this video from years ago https://youtu.be/OQPzas965Kg?t=61 but is kinda outdated, if you wanna see the addon by yourself I suggest downloading it from curse.