For starters since it is obvious UBI can get rid of the lower end of wealth distribution (which is the whole point if the fear is mass unemployment) but we don't want to have UBI be all funneled to the top percentiles it is obvious we have to set artificial limits on wealth accumulation. Now we get rid of the bottom end of wealth distribution (no job, no income) but we also get rid of the top end of wealth distribution (can't be filthy rich, past some point your marginal taxation quickly approaches 100%).

Second, it is important to distinguish between unconditional basic income and basic income that is only handed out if you are unemployed. If people can get UBI + income from work then social mobility is much easier to be achieved. Then there is the amount of UBI each person gets: if UBI is for survival only then you can't use this for investments because it is hard to save. If UBI allows you to save and eventually invest in your own business ventures then social mobility is easier again.

Third, if we are implementing UBI because of mass unemployment and then only those who get UBI + income from work can have decent social mobility, we would need to allow more people to work in a world where work is increasingly scarce. This means we need to reduce the amount of hours people work, so that more people can work, less working hours > more people working.

Further, if we transform medium to large private enterprises into cooperatives, then funneling UBI into companies is suddenly not a wealth concentration trap, because cooperatives distribute profits among workers instead of small quantities of shareholders that own majority of shares, and to the top of hierarchies via agency-theory solutions.

Finally, if better distribution in this system generates hyper Inflation in basic necessity goods and services, we degrow superficial industries to control Inflation in basic necessities via supply elasticity.

That's my view but what do you propose?