I've discovered something about how sats and WPs can work together, quite by accident. The usual way to take out a well-defended planet without losing a lot of ships is to stand-off and fire swarms of missiles until the WPs are destroyed, then you can move in and deal with the sats without being pasted by Massive-mount direct-fire weapons.
Well, I have modded my config files, and I recently ran into a planet with lots of satellites containing POINT-DEFENCE. This created a problem for my waves of missiles. The range of the PDC was enough to cover the planet no matter which direction I sent the missiles from, but missiles can NOT target satellites! If I went in close enough to target the sats with other weapons, I'd be exposed to the high-powered ground-based weapons with much greater range than my ship-based weapons. In this case, there were not enough PDCs on the sats to completely overcome my missiles, and I eventually destroyed the WPs and closed in to finish off the planet. But if there had been more -- like sats had been deliberately filled with PDC instead of just some added as secondary weapons -- things could have been very different. I think this is the clue to a very powerful defense strategy. Build satellites full of PDC and only a few with standard beam weapons and/or missiles. Put your heavy weapons on the planet and your anti-missile defenses in orbit. If you have the time and resources to build this up it could be a deadly combination.