Exporting only certain lights and their reflections

I’m planning a project where I need to create a composite that allows me to export specific lamps, emissive materials, and their interactions with the world, visible to the camera separately.

The basic idea involves aluminum GUI elements with glowing text.
I want to export the aluminum elements and the sun as one image sequence, and then export the glowing text along with any additional lights and their bounce lighting effects on the aluminum as a separate “light pass.” This way, I can overlay the aluminum elements with the light pass as a WebM video with an alpha channel, giving the user the ability to change the light color themselves on the website.

I haven’t started the project yet, but I want to make sure I structure it right before I start that’s why I’m asking the question first

This isn’t an answer, but a tip:

Safari supports HEVC with alpha, and Chrome does not.

Chrome supports VP9 with alpha, and Safari does not.
As of Safari 15 in macOS Big Sur, Safari has VP9/webm support. But not for transparency.