The ability to modify the code is a central tenet of free software. The GPL takes care of making those modifications available to others. That effectively is the payment the original devs get.

If companies are required to pay, then the software is not libre. I understand your intent, but this isn't a solution (even if it was, it would just mean that it would just be a tax for small companies, Meta and Alphabet aren't worrying about a tax), building a stronger community is.

Commercial software is not mutually exclusive with libre software, and things like copyleft exist to prevent companies from using libre software to create proprietary software.

The overwhelming majority of the kernel development is heavily company financed. Are you saying that despite that, the very developer should get the stipend?

Lets make one thing clear, exponentially increasing wealth/power the higher you are in society is a pretty heavy general rule of thumb to beat, whicever way you try moving the seats.

Making such a system for devs will make a pretty wealthy class of people even more privileged with de facto rules that wont apply for the rest of society more in need of money and freedom, meaning actually owning the share of income from their work even over the pay the receive from the company.

Making this a general rule for everyone will more like reshuffle thungs but the exponentiality will in some form persist. If you inevitably fuck it up the implementation phase, it wont get better any bit. You will have the same miserable pay except you own your work. So what.