For example, ask for a 4 day work week, or 2 months paid leave, or possibly other perks that are important to you?
You could also ask that the company make a donation on your behalf to another cause.
The nice part is that you can look passionate, important, and pragmatic all at the same time.
For example, say "I deeply care about free and open source software. As part of my compensation package, I expect your XYZ company to donate $$$ to MyCause."
Then there's always the "unlimited time off, we trust you".
But that's exactly why I want my 80% time to be officially recognized. I don't want to feel guilty or worry that I haven't justified my existence when I'm not there on Fridays. The contractual 3-day weekend means a lot more to me than an extra 20% salary with strings attached.
But regardless, seems pretty awesome. I would want employees to get work done, not sit in a chair. I suspect someone working 4 day weeks would get more work done, per hour average, then someone working 5 days a week. Seems a no-brainer for a business to allow.
Now 1-2 day weeks for 20-40% pay? I can see communication is a bit tricky.. but 4 days a week is plenty.
But a lot of times there's actually a specific field in the application form with "expected compensation".