Theme building guidelines & process?

[Milanzor]

The current CSS structure does not really support creating new themes.

Currently, in the src/client/styles folder, there is a themes/default folder. The files in there are always loaded and used as the theme. There is no way to make a new theme without either not loading the default theme or loading the default theme AND a new theme, having your own theme overrule the default css variables.

Also there is no way to tell JARVIS what theme to use when instantiating in a Webpack config.
Wouldn't it be great like this:

new Jarvis({
    theme: 'light'
});

What is the expected way for someone to make a theme? I have some idea's but I'd be wasting time if you already have work in progress for this.