As a cofounder of a very small company (8 FT, 2 part-time, 2-10 contractors varying by season), but one with a longer life than many startups newer than us (10+ years since our first revenue), I have been trying to normalize long-term part-time hires in all critical roles for some time now at our org.
Yet, it is hard to overcome the cultural energy around the implications "part time = low impact", "part time = temporary", "part time = mercenary", "part time = lazy", "part time = not passionate". This sentiment arises from colleagues, investors, leadership, customers, and hell, the part time employee themselves at times (some kind of internalized contempt for wanting/needing/preferring to go part time).
My partner just got their role converted to part-time starting March, after consciously coming to the conclusion that it was the only healthy way to remain in their career, despite not having children. They still processing to get over the feeling of guilt and of being less-than somehow for not being okay with handing over their full cognitive capacity and waking hours, especially without being an "accepted exception", ie someone with kids, being a caretaker, or a person with a (visible) disability.
I want to live in a world where people can passionately work on something as part of a team, long-term, while being fairly compensated for that work, for less than 30 hours a week. If possible, I myself want to have that level of involvement even as a cofounder or leader of a business/project/organization so I can give my diverse passions the attention they deserve, without it "being weird" to my cofounders or other teammates.