I'd present this to the employer as switching from a full-time employee to an almost-full-time consultant. They give you a project, you get it done, regardless

I'd present this to the employer as switching from a full-time employee to an almost-full-time consultant. They give you a project, you get it done, regardless of where and how you do it. If the employer needs more convincing, propose you start with a test by trying one day per week remote from now. Agreeing to take a pay cut would be the icing on the cake.