I've been thinking a lot about how no matter what constitutes “full time,” some companies will always try to keep people under that threshold to deny them fair pay and benefits. So I think the solution would be to pay overtime for part time work.
So under the current system, 40 hours/week is full time and anything under that is part time. But I think that if full time is 40 hours, than any part time worker who goes above 20 hours in a week should be paid overtime for each hour over 20. Just like how full time workers who go over 40 hours/week get overtime. This would still work if we reduce the hours in the work week, just whatever you work over half of “full time” would be paid in overtime.
I think it would help prevent companies from overstaffing part time workers. To me, part time shouldn't mean one or two hours under full time, it should mean working substantially less than a full time worker. But I'm also not sure if part time and full time would even be important distinctions if we won things like UBI, universal healthcare, and guaranteed paid leave, so maybe it's moot. What do you think?