I tried a jack many many years ago. It soon became obvious that it was not a practical solution for a router lift. A lift needs to be able to raise a router in small enough increments to allow precise adjustments. The acme screw on a jack is fine for lifting a car but it's not capable of raising a car 1/16th or 1/32 or 1/16th of an inch. With router work, it's often necessary to adjust the bit by a few thousands of an inch.