Our societies are complex, but the job market idea is bone simple. Divide the amount of work among those seeking it--shortening work hours so everyone has a job? Let individual workers decide what the work is worth to them, making prices fairly reflect the human cost of production? Do this by taking away the legal right of employers to set wages and work hours? Technicaly, these are all fairly simple to carry out, although the software would be complicated.
The question we're trying to answer is, in a complicated industrialized society, how do you arrange work with minimal exploitation and maximal freedom, without losing the organizational and productive capacity which creates many benefits that we want. (Some solve it by saying we don't want an industrialized society, you know, no airplanes if people don't want to make them. I'd say we do, but if the work is unpleasant it should be well-compensated, accurately reflecting the cost those workers are paying--the pain, the risk, the boredom, etc.) And, we want to know, how do you do it in such a way that the population at large can decide the course of their economic lives, not just individually, but collectively.
With a job market the public can vote on--and credibly expect their decisions to hold--the length of the work week, the ratio of maximum to minimum wage, the average work year length (in effect, whether the economy should grow or shrink--overall production), and the rate of profit (if any), along with things we already are supposed to be able to make decisions about like taxation and publicly provided social benefits.
There's this idea that the only way you can have something like an aircraft factory is under capitalism or, as they call it, 'command socialism'. In other words, people have to be organized into doing it, probably coerced, and that's just the way it is. No coercion, no aircraft. (This primarily comes from a negative view of work, and the view that management or coordination, rather than being another job, is in its essence about power over others.)
So we need to talk about how socialism can be arranged in such a way that it would actually be something we'd want to live in. Abolish the wage system, and then? Many people, even leftists, think socialism is a good idea morally but they're not sure they'd want to live there, they think it will involve, inevitably, a bloated planning bureaucracy (or endless work meetings), unchanging jobs, not much creativity, no new laptops, or that it would be chaotic, unorganized, and unproductive. However right or wrong we may think this is, we have to talk about what's necessary in that, and what isn't. As our ability to manage information grows, it's created possibilities where before we had to make compromises, and I think that's where the job market idea breaks new ground.
As for viability, here I'm going to interpret you to mean political viability. I'd say all these "models of intermediate social orders" have one goal right now, and that's educational. The role of such work is to open up possibilities--what functions do we want our economies to perform, and how can they be performed better?--since the dominant view is that currently-existing capitalism is a force of nature, or perhaps an act of god.
Jenny Brown (there's more on the job market at http://www.jobmarketbook.com)