I've basically gone ahead and changed the way the entire mod works!
Thanks to @13Stewartc for explaining how @aljowen 's manifold glow code works and giving out the html as a base to work on, I was able to eliminate the "stages" in the glowing of the brakes.
However, this has it's limitations. Due to it being HTML, the glow texture can't be transparent on top of the normal brake, instead I have to replace the brake texture's colour map. To make the glow visible in the dark, there is a noticable switch to an emissive texture at 375 degrees. That is so that the brakes arent emissive 24/7.
This is the best that can be done until translucent HTML textures are a thing.
Above that, the Hopper Crawler now has brake glow!