Or we could do like before: let the church help the poors, the nobles take decisions and the peasants make the food. Like that, everyone has its clear and simple role and you wont complain of taxes: you ll have no revenue :)
So long as any profits from these investments are not ploughed back into general revenues, your concerns are moot. For example, you could establish an independent body—let's call it INVEST1—to oversee these investments. INVEST1 would be required to divest ownership of successful enterprises at a threshold that ensures money spent roughly matches money earned (and thus self-funding). Once it reaches a stable equilibrium, you spin off INVEST1 as a fully independent not-for-profit. Government then establishes INVEST2 and the process starts again from the beginning. Rinse and repeat.
So when people build off humanity's past knowledge and they pay for the privilege I assume the new knowledge that is created does not belong to humanity any longer and belongs to individuals?
https://sbir.nih.gov/about/what-is-sbir-sttr
neither were at play here but the idea is pretty darn normal.
The money will be made by private companies that have no connection to the researchers who received the grants, but simply use the published research in something they build.
It's hard to see a good way to build a system to make the private companies pay back the grants. It would be an accounting and tracking nightmare to try to figure out how much money is actually being made from the research that any given grant paid for.
There’s a reason for the saying ‘standing on the shoulders of giants’
Perhaps with some interest, since the grants are high risk (many grants fail)