This is super cool! Pinouts and wire colors are only part of a harness, though. Other things I care about:

Branch lengths and locations, where individual connectors branch off the main trunk of the harness.

Terminal types, because a single connector sometimes has different terminals per pin position, or per wire type, or other requirements.

Custom wire colors and gauges; multiconductor cables aren't always all the same gauge.

Inline splices (these may be implementable as a special case of a connector where most wires just pass through and just a few join on one "pin"?).

Is there a WYSIWYG or live-updating editor so you can see the result as you edit the markup? I understand why it's written that way, but it'd be a lot of work to translate certain harnesses to be expressed that way.