I'd use an existing programming language (asymptote or scala) and build a framework to create a bunch of EPS/PNG/SVG icons.
No new file format....
This is what I mean with DSL:
No new file format....
This is what I mean with DSL:
Hint: they use Illustrator. They're going to keep using Illustrator. They're not going to stop using Illustrator so you can have a marginally easier Github workflow.