Then it's not Open Source.
I agree that funding Open Source software is hard, and I want a solution as much as anybody: It's not even a theoretical problem for me, I am currently self employed and would really like to fund myself with just Open Source software.
What you're describing is a really bad idea though, it isn't actually FOSS. Heck, it's actually considerably worse than many of the other licensing models out there, because it basically boils down to being a subscription service. Many of us are involved in Open Source because we specifically hate the 'software rental' model.
Better ideas that I've seen people kicking around that I wouldn't immediately dismiss:
- putting a paywall in front of issue trackers
- dual licensing under the GPL and a proprietary paid license.
- requiring upfront payment for new features (ie Kickstarter/Patreon)
- open core models (ie Gitlab's strategy)
- advertising and sponsorships via READMEs and official sites.
Many of these ideas also have problems, but at least they don't require us to completely abandon FOSS licensing.