These are the side-effects of having to use the branding kit to get HTML files added to router. What's annoying is that netinstall cannot copy the same files. And since you cannot run this code on another server since you'd run in CORS restrictions and need to use a "CORS proxy" (see Using Caddy Server as CORS Proxy for REST API for example).
So I can see how you're left with branding - which comes with the associated side-effects like needing to change defconf (or have a more complex install process to deal with scripting part separately).
Agree. I saw this in the docs too. In branding, this become the platform in discovery.
It's transpiled from TypeScript (using React libraries), so imagine it be very unreadable... OP has the source on GitHub, so you may better offer "compiling" it and creating the package yourself...