Rotation of employees can be done; however, you should be reminded that it should not diminish the salary and benefits due them. Under the labor code,there is a prohibition against non-diminution of benefits which means that any schemes which would lessen the salary and benefits which have been regularly given to the employees are unlawful. If rotation would be done simply to maximize energy e.g. electricity then this can be allowed. However, if this will reduce say the working hours or days which ultimately affect their salaries, then this is a violation of the labor code.
There is no specific rule that either allows or disallows payment of separation pay in staggered basis. As long as the employees agree in writing and the scheme is not disadvantageous and shocking to the moral conscience,then, it will be allowed.