Separate def files? Auto-generate hover styles on everything? Some marker in the manifest? Five points, because we need some exploratory work before deciding on a plan and implementing it.
Shorlander and I agree that we can add classes to each <g> element, and the tool will loop through them, and output one image for each class.
And here's the code that implements that: https://github.com/bwinton/svg-magic/commit/37aa4c6e00b0b3607853bbb64218e184cc56e4c3