What happens if the business makes no profit? I'm assuming that employees won't have to cover a percentage of the loss in that case, but if this money is meant to make up for low wages, it will fail in the face of a loss.
What happens if the business cooks the books to make it look like it didn't make a profit? Note that this was such a common problem in Hollywood productions that star contracts now routinely require a percentage of the gross revenues rather than the net profit.
And now we get to the hard part. Let's think about what we are trying to accomplish here. We want to increase the wages of the poor. In this system, the well-to-do would use their natural advantages (connections, resources, etc.) to grab the best jobs with the highest profit sharing. The poor would get the jobs at marginal businesses that never quite make a profit.
This is especially annoying in that normally lousy jobs at profitable companies would become lucrative. Of course, an easy fix for that would be to switch from direct hires to contractors. As contractors are not employees, they wouldn't share in the profit sharing. We can see examples of that now with the ridesharing companies Uber and Lyft. They evade employment laws by utilizing self-employed drivers.
So instead of hiring janitors in-house, companies will hire cleaning companies. Instead of hiring software developers, they will hire other companies. Those companies will make small profits, so they will have to share only a small amount. The hiring company will make big profits and evade paying more than the minimum wage.
Should someone who works five hours a week at a company get the same profit sharing as someone who works fifty hours a week? What about someone who only works for a brief period of time? Same amount as someone who works all year?
Not quite that profitable
But on the other hand, some corporations are reporting tens of billions of dollars in quarterly profit.
This doesn't seem to be true. The most profitable corporation had less than $40 billion in profits. That's not even one ten of billions per quarter much less multiple tens.
Another problem is that even if it is true, those corporations won't necessarily employ the relevant employees. Even now, most McDonald's restaurants are owned not by the corporation but by local franchises.
Berkshire Hathaway is an especially interesting example. It's one of the most profitable companies in the world, but it is a holding company. For example, it owns 26% of Kraft Heinz. Do the Kraft Heinz employees share in the Berkshire Hathaway profits? Do multiple levels of employees share in the Kraft Heinz profits? What about wholly owned companies like GEICO? Pooled employees or separate employees?
Note that corporate headquarters has fewer than a hundred employees. Should they be the only ones to get the profit sharing? If not, how do we keep them from doing so? What's to keep them from reducing their ownership share of each company to just below the trigger amount?
Increased capital prices
A side effect of this would be to make capital returns smaller. So it would be harder for companies to raise money. It's essentially a tax on capital and a credit for employees. Of course, companies could compensate for that by reducing salaries and wages. Or by increasing debt financing. Presumably interest on debt won't be shared while dividends on stocks come out of profits.
Currently if you have a profitable company, it can make sense to invest some of those profits into expanding the company. Even if the new growth is less profitable than the old, it can still increase total profits as it decreases average profits. But under this system, employees are incented to increase average profits per employee rather than total profits. Companies that fill small but profitable niches will be more desirable to employees than large, diverse companies.