The experience of the former Soviet Union would tend to argue against this thesis.
The system I've described bears very little resemblance to the Stalinist top-down command economy. Of course to make it practically workable we'd have to take all sorts of extra measures that the OP did not specify I suppose. But all of these can be handled very differently than the Bolsheviks desired. There are no Ministries of various industries commanding specified outputs from specified inputs and taking all decision making away from the individual firms here. Here we have a mix of private and worker investors sharing ownership of the firm, with no state intervention (beyond skimming all individual assets beyond 1935 $ 8 million) dictating anything. Thus the dynamics of the Soviet Plan system and this have little to do with each other.
You wouldn't get sudden radical impoverishment but would get an economy that was less nimble, more risk averse and less creative.
But why should that be? What we might have instead is tens of millions of investors, who have a lot less than $8 million, seeking to multiply the value of their capital considerably below that limit. This puts up money for lots of competition. Firms that are less nimble, more risk averse and less creative will still be crowded out by others that are more aggressive. The fact that seeing an individual limit that successful investors approach removes the most successful from the pool may result in a degradation of collective wisdom, but the fact is OTL market players who have been in the business all their lives wind up collectively doing very stupid things; I think any falling out of experienced players leaving the market run by neophyte amateurs would have any bad effects of that more than offset by the sandwiching stabilization of the pool of idle rich trickling wealth down from above, and the pool of guaranteed minimum income sustaining markets from below.
Again this is not a Soviet command economy. It might be something like syndicalism, which I have not studied very closely. It isn't Marxist in doctrine, in that there is no desire to eliminate the dynamism of individual wealth accumulation, merely to cap it at levels far above anything the pool of the working class can reasonably expect to attain.
Some criticism mentioned that perhaps the $8 million cap will not be raised with inflation. Still, how many of us on this board could possibly hope to end our lives with $8 million, 2017 dollars, in assets? Raising the cap with inflation is probably a good idea and would probably get democratic approval, but even if not, little harm would be done.
I don't love the very rich -horrible shits most of them- but they have two very important social functions based on their surplus capital. As the source of investment capital for new technologies and techniques and as early adopters of new goods and services before their provision is streamlined enough for the ordinary man in the street to be able to afford them.
They aren't the
source of investment capital. The source of investment capital is producing goods at lower cost than their value, measured as the socially necessary labor time to put another increment of a given commodity on the market. They
manage the investment capital. The
workers doing their jobs are the source of investment capital, along with being the source of the goods and services socially necessary to consume.
In the form of STW I laid out above, what happens is that the largest holders remove themselves from the system, except as passive consumers, but other people who have not yet managed to come within close range of the asset ceiling remain motivated to seek opportunities to profit from new technologies and new techniques. New goods and services are going to fall into the categories of capital goods--that is, items or services that relate to the productive process, and the hungry legions of small investors will batten onto those, probably earlier and with more aggression than the very comfortable and powerful centralized gigantic capitals of OTL do. And consumer goods and services, which people with wealth in the ballpark of over $100 million will be well fixed to purchase for their own gratification.
Workers you see continue to be exploited. But they accept this, because realistically the high productivity of modern industrial techniques does require both centralized management and a rather ruthless drive to keep costs, including labor costs, in check.
In a sense--in the sense any laissez-faire system will lead to massive social injustice and discontent--the welfare of the working class is in contradiction to the demands of the system. Capitalism can operate on the backs of a deeply miserable working class, with the effective market demand mostly coming from the gratification of the rich minority, and with the net cost of maintaining the workforce being a minor line item in the whole.
Don't forget--Wehrner von Braun operated Camp Dora to make V-2 rockets, some of the most advanced weaponry then extant on the face of the planet, requiring not only dumb labor but skills such as draftsmen had to provide, with a workforce they didn't even
feed. This is admittedly unsustainably low, but it doesn't have to be much more generous to be sustainable. That is, if we omit the matter of politics and the weapons workers have in the class struggle.
Vice versa though, workers have definitely not shown the all-conquering capability to brush aside the bourgeois classes and simply run everything on their own behalf for motives of pure communist solidarity either. In my perception the biggest blind spot and area of failing Marxists have shown is in the field of politics. On analyzing and predicting the operations of competitive capitalism they have been spot-on with a far better track record than the so-called economists of mainstream academia. On predicting, let alone mobilizing, the political behavior of proletarian masses, including their actual response to a Party run socialist order, they have fallen quite flat on their faces.
STW is a muddled compromise which remains fundamentally capitalist in its operations and assumes capitalist motives continue to drive the working class too. The working class majority supports it because their worst (and entirely legitimate, under our current system) fears are addressed, the carrot of becoming one of the idle rich via the path of honorable workplace accomplishment remains fixed before them. It is only if one believes the stick of absolute poverty that is the lot alike of bad workers who don't fit in or step out of line, and perfectly good ones who just happen to be surplus to the new technologies and new techniques is also vital that capitalism cannot afford this sort of paternalistic social welfare.
Will the poor in fact also sit idle, refusing to show up and work in factories they might well own a share in, because a minimal income is guaranteed to them? To an extent, this merely adjusts the size of the workforce to come in line with the higher levels of productivity available. But I think the lure of having more via wages, and even eventually having enough independent wealth to sit it out in style, would be adequate to keep the wheels turning, and the funds for investment that used to come down like manna from a capricious and greedy pantheon of the super-wealthy will now well up from below.