The approach I have come up with which I cannot believe should be unique or even my invention is to budget against my time. At the moment, my service has £0 revenue so I need to give 80% of my time to “the suits” in order to pay for everything. I need to get to £X revenue before I can get away with giving 0% of my time to “the suits”.
You may then think that this means I have 20% of my time to go toward increasing revenue, but that is just the most conservative option. I could find a way to loan myself 40% time (go down to a 40% contract, or take a 100% contract for W weeks in return for giving myself 1.5*W weeks of focus, or something else) on the understanding that I will “pay back” that loan by either increasing revenue, or by paying off the debt by doing more work for “the suits” later.
All that really means is that I’ve given myself a way to increase the number of steps between the two extremes of “work until I’m making enough revenue not to work” and “not work”.
Edited to add: yes, being able to go part-time is a privilege, I accept that, but it is more accessible than people realise. I went from 100% to 80% by asking my manager and being told “yes”, with no resistance from them and just a bit of negotiation over what would happen to 20% of my job and how holiday allowance would work. Many people who do not believe their managers would allow them to go part time, including myself up to that point, have not yet asked.