2500CHF per adult is an enormous proportion of national income to redistribute: even taking into account Switzerland's unusual prosperity we're talking about an income subsidy that's nearly 40% of per capita GDP. That's a huge sum of money that's going to have to be found via the tax system, and it's far too big to find from merely taxing the top end (especially when you're as full of millionaires and as prosperous from foreign capital flows attracted in part by your low tax regime).
It sounds likely to be a huge boon to certain categories of "idle rich" dabbling in low end residential property speculation (CHF 2500 per month average Zurich apartments aren't going to stay that way when even unemployed couples earn double that) and ironically probably penalise precisely those employees most readily exploited by employers: those without the raw ability to earn above the median wage but with the work ethic and drive to get close.