What you could try to do is have them remove the W4 on file and, if they won't, offer to sign a waiver of liability for them regarding the IRS. I think technically a W4 must be renewed every year or every few years, but I'm not sure about that one.

What Kelly does is easier (except that you still pay into SS/Medicare) - there is no need to try to remove the W4. You will just be sent a refund from the IRS of any unfiled taxes within the past 3 years. You can then start filing EXEMPT. I take home ~85% of my check and it will be ~90% once my state gets rid of its income tax laws in a few years. Some states honor lawful money, some don't. But in federal it always applies.

To be very brief, lawful money is not taxable, so you are using 12 USC 411 to demand lawful money for your FRNs. Nothing changes physically, because the cash in your pocket can be used as both. But on paper, and in your bank account, is where things "change". What is changed is how they money is viewed/treated.