Luckily the scenario of "employers wield all the power" you describe is so far from reality as to be irrelevant. In theory, employees need a job but they don't need this job. Turning it down is and taking a different job is always an option - that's why virtually no jobs actually pay the minimum wage.

You are somewhat right, however - a BI will give people the ability to turn down all jobs. E.g., in the last BI experiment, work effort was reduced by 13% - more than double the effect of the great recession.

A much better solution is the Basic Job. You get a Basic Income (which pays less than any job in the market economy) but you need to work for it. You spend a lot less money (anyone working in the market economy doesn't get paid by the basic job), you have minimal disincentive for getting a job, and you get some productive output (e.g. parks have less trash).