> How come I never see any concrete proposals for how to equitably distribute the wealth of AI?
Probably because most politics about how to "equitably distribute the wealth" of anything are one or both of "badly thought out" and/or "too complex to read".
For example of the former, I could easily say "have the government own the AI", which is great if you expect a government that owns AI to continue to care if their policies are supported by anyone living under them, not so much if you consider that a fully automated police force is able to stamp out any dissent etc.
For example of the latter, see all efforts to align any non-trivial AI to anything, literally even one thing, without someone messing up the reward function.
For your example of 10%, well, there's a dichotomy on how broad the AI is, if it's more like (it's not really boolean) a special-purpose system or if it's fully-general over all that any human can do:
• Special-purpose: that works but also you don't need it because it's just an assistant AI and "expands the pie" rather than displacing workers entirely.
• Fully-general: the AI company can relocate offshore, or off planet, do whatever it wants and raise a middle finger at you. It's got all the power and you don't.