Option is to make all employees 28 hr/week employees. Should be a large pool of applicants as companies all over the spectrum will be dropping full time employees.
Other way is to fire all employees and contract with employee leasing companies to supply the labor. Hire enough of these leasing companies so that no one company is responsible for no more than 49 people, keeping their ranks below the magic number!
Actually, the idea of just using temporary employees might work.