I quite understand that there is a tendency to marketise decision-making in an unhelpful fashion, but I’m not entirely sure how this scheme is too much of a problem, beyond using the word “tokens”. Could you elaborate as to the specific problems of this scheme as opposed to those of general attempts to marketise?

And “quadratic voting” may have uses beyond the areas governed by the US constitution. Even within those areas, there are minorities other than property owners. Blacks, for example, do not seem to have been very successful as a minority in preventing the various things that the state does to them that are plausibly unhelpful (though the quantification thereof may well be intractable). The particular use case here, however, seems to be to make the specific institutions you describe more effective, as opposed to relying on their being pitted against each other to make things work. I think that it is more desirable to have a single institution that works well, where possible (which it generally isn’t) than multiple institutions that operate against each other in an attempt to avoid pitfalls, because one generally falls into more pitfalls in the process, even if the balance of advantage lies with the latter case.