Capitalism is Opposed to Human Happiness Debate, Volume 2
The employees' interest in the company is the same as any other share holder or investor: it provides them income, or livelihood. That's the purpose of a company to both employees and share holders (investors). If the company goes bankrupt they loose their livelihood, and as shareholders, they also have the responsibilities, obligations, and debts of the company. Losing a job is the same as losing the income from dividends.
If employees are the only shareholders, then the "investor" is really a creditor, like a bank, and has the same influence that any non-shareholding creditor would have today. I guess the question is whether this system is open to entice investment by offering shares: apparently not if the only share holders are to be employees. The worker-cooperative is a different system then the one based on enticing investment by offering shares -- they bargain collectively, as a unit, for what they need and what they are willing to give for it, and whether they're willing to give away decision power to an investor, as would be the case in selling shares.
I personally believe in democratizing the economy within the framework of capitalism by looking at the country as a land owning company in which each citizen has an equal share, and is not necessarily an "employee". The income of this company comes from collecting rents from residents, and the land can be managed by wage earners, whether or not they are share holders. To avoid a land-owning monopoly, perhaps there should be a limit to the land area of such a country or company.
You are right about providing income. But shares usually have a price which is a measure for future dividends. So if the company goes bankrupt investors loose future dividends (which is property, not income). In this system however shares have no price, they only represent a right for participation for employees. An employment is not property, its just a contract which can (luckily) be canceled. You don't have to sell it when you leave.
how do they look like?
Shares are property whose only value is in providing income, and the only reason you can sell them is because someone else thinks they can derive income from them. So if a company goes bankrupt, investors loose their income, present or future, as does the employee. Perhaps an employment is not considered property, but it can be: Jobs can be (and are, sometimes informally/illegally) bought and sold. The catch is that the job usually does not belong to the employee, so he's generally not the one who can sell it. So he does not have decision power over his job, and his interest is solely in the income it provides. But those that do have control of jobs and can buy and sell them, i.e. share holders, can only derive value from them directly or indirectly because of the shares' ability to generate income, so the bottom line is income.
BTW the purpose of unions, collectives, and worker's cooperatives is to give the employee/worker, this decision power over his job/work, in effect "ownership", though it's not identified as such. Also, you don't "have to sell" shares when you "leave", and property, like employment, is also "just a contract"; it's an agreement to provide a share of the profits (in exchange for the capital investment -- similar to an agreement to provide a wage in exchange for work: an "investment of sweat")
How does any responsibility, etc. look like. Who's is responsible for the company's debts? There might be legal gymnastics that separate and alienate the shareholder from the company's responsibilities, but ultimately the owners of the company are the responsible parties, the same way you are responsible for any other property you own.
There's a third problem. You stifle hard workers. They become disenfranchised because of their inability to excel and be justly rewarded. The system will decay into inefficiency.
If a company does badly, generates losses and goes bankrupt, investors lose the capital they invested in the company. An employee doesn't lose any capital - he merely has one fewer buyers to sell his labor to. He keeps his body and skills and can go rent himself out to another company.
Being employed is not an investment in a company, it's a rental, much like when the company rents office space.