It incredibly expensive, a satellite that could be lift by a Falcon 9 with a first stage only recovery would have to be lifted by a Falcon Heavy if you wanted to recover the second stage. Basically you'd need to almost double the unfueled weight of the second stage with aerodynamic devices that can withstand the re-entry plasma and the heat shield. And then add the extra weight for the de-orbit and re-entry burns. You would probably more than halve the payload capacity. Even at best is borders on not worth it.
[EDIT] fixed typo