Forcing rich people to invest in low return area might be better strategy. If they know how to make money productive, they can make that area grow faster so that gdp can grow faster.
This will ensure rich people money grows at higher rate only if gdp grows.
Asking government to manage money is very in efficient.
But I think we're not even on the path to creating AGI. We're creating software that replicate and remix human knowledge at a fixed point in time. And so it's a fixed target that you can't really exceed, which would itself already entail diminishing returns. Pair this with the fact that it's based on neural networks which also invariably reach a point of sharply diminishing returns in essentially every field they're used in, and you have something that looks much closer to what we're doing right now - where all competitors will eventually converge on something largely indistinguishable from each other, in terms of ability.