Supposedly Athenian taxes were assessed this way. The government handed out a list of tax obligations, and if you thought your tax requirement was heavier than somebody else's who was richer than you, you could challenge them. A challenge meant they could choose either to swap tax obligations with you, or, if they didn't believe you were poorer, to swap all their assets for yours.
Usually it's done if you challenge a ticket and they still find you guilty. Then they may adjust the fine relative to your financial condition. (I'm not sure how they find that out, eg if they talk to HMRC or other).
https://en.wikipedia.org/wiki/Day-fine
I don't think the UK does it much, except in the sense that if you lose a case you're liable for costs, and for a driving offence judges are more likely to apply a statutory criminal fine.
Smaller offences have an upper fine limit, and that won't be raised based on income. But it's always bigger than the token Fixed Penalty Notice fine you get from the police. Serious offences have unlimited fines, so judges can get more creative with financial penalties.
As for the proposal, I'd be for it. I make enough that under some circumstances I very well might just pay the $35 than drive around looking for a parking space. When I am in a car, though, it's usually in our ten year old Scion that cost $20K brand new, so I don't know that would it would be such a disincentive for me (and my illegal parking is a rare occurrence regardless, and usually by accident), but might work for the general case.
