It's super trivial to outsource the sub setting to Google Fonts. Just request their CSS and curl the font files referenced in it. If that is too tedious, build a small proxy.
(And in my case that whole effort wasn't actually so much for philosophical reasons, i.e. to try avoiding to use Google at all costs, but rather because Google Fonts was serving an outdated version of the font I was wanting to use, and was missing either some additional characters or bug fixes that were only added in a more recent version.)