I think what you've outline here is entirely theoretical, unless you have some empirical evidence you have thus far not linked, and (IMHO) likely not correct.
I also don't think there would be any particularly progressive or otherwise good effects from reducing stock buybacks, but assuming we did think that, we can skip all of the wealth tax second/third order effect theorizing and just use a direct corporate buyback tax, which we did do in the IRA. Stock buybacks have already fallen, but if its effects are not big enough for you, then raise it or reduce exemptions. Not that I think that anything particularly good would come of that.
I also don't think there would be any particularly progressive or otherwise good effects from reducing stock buybacks, but assuming we did think that, we can skip all of the wealth tax second/third order effect theorizing and just use a direct corporate buyback tax, which we did do in the IRA. Stock buybacks have already fallen, but if its effects are not big enough for you, then raise it or reduce exemptions. Not that I think that anything particularly good would come of that.