"Is moving these valid business expenses going to make my client more prone to an audit on his state tax return since his unreimbursed employee expenses greatly increase?"

What you want to understand is that "valid" and "business" do not by definition go together.

Everyone who works has expenses for working. That doesn't make them business or write offs.

The tax regulation wants you to match ordinary costs against that income it earns. As a business, that is a stand-alone proposition. As an employee, your employer is considered as incurring costs of being in business.

If an employee uses their personal vehicle to do the work of the employer, there is a provision called An Accountable Plan. The employee turns in a mileage report, and the employer reimburses under the IRS mileage rates. If they do this (or less), it isn't even taxable to the employee.

"my client has valid mileage, uniform, and continuing education expenses."

You keep using the valid as if that changes how something applies to something. You can read what the IRS states about job-related education and how the employer can cover some of these types of costs. These rules have been recently expanded. Nothing prevents the employer from requiring uniforms, and then stocking them for the staff. "Uniforms" is not street clothes or clothes worn for every day use. It would be specialty items, safety items,etc.

You don't "move" things around. You put them where they apply. There either is a provision for it, or there isn't. It might not be what you used to do. It might be better.

Even if your taxpayer has no one issuing an informational reporting form (1099-NEC), that doesn't mean they are not also in business independently of that employer. But you can't move everything they incur, to the Sched C. The employer-related costs are not Sched C. Only expenses incurred to earn that Sched C income, are part of Sched C reporting.

This part has not changed, from prior years.