Compound unit types?

Would it be worthwhile to allow combinations of different units, e.g. a length expressed as 6'5" or an angle as 4°45"10'? I'd be happy to create a PR with this, but maybe it exists already, has been tried before or is otherwise known to be a bad idea? Happy to hear your thoughts.

The issue proposes supporting compound unit expressions such as feet/inches and degrees/minutes/seconds, but names no files, tests, or entry points. First check whether this capability already exists or has been attempted; done would require a settled design and an agreed implementation scope.

Written by the indexing model from the issue text.