Reusable launch escape upper stage based on Dragon, to save expensive payloads

[mme]

I have never been up close to a satellite before, but judging from pictures they look like large sensitive boxes

I would not image a large sensitive box would fare very well during a LES firing, chute deployment, then splashdown into the ocean.

If a satellite is lost, call Jake from State Farm.

Would all of it be destroyed?
CST-7 is already an example of how an activated LES would have saved several hundreds of millions of dollars of payload value. I don't understand how you guys try to pretend to not understand this.

The sea water problem can be avoided by not launching across a sea. Did that kind of thought never enter your minds? Dragon is designed to soft land on dry land. Do I have to draw an illustration with crayons for you to get that concept?

Total non-sequitor.

1. All rockets launch over the ocean for safety reasons and basic orbital mechanics.
2. Unlike CRS-7, satellites are not space capsules designed to return to Earth.
3. Really expensive satellites tend to be at the upper margins of the rocket's abilities.  Adding tonnes of rocket fuel, engines, parachutes, and some protective enclosure means never being able to launch the things on a Falcon 9. But it will waste millions and millions of dollars every single launch and probably actually add more failure modes.

This has been discussed ad nauseum in other threads. Please consider reading those. Also, this is not SpaceX specific.

[whitelancer64]

It's not worth the cost. Both satellites and the rocket would need to be substantially redesigned, as has been pointed out by several people, for events that are (mercifully) fairly rare. If rockets were blowing up every other launch, it might be worth it, except if rockets in general were that unreliable, then why would the launch escape system be any different.

In summary, to your initial query, "wouldn't it be worthwhile..." the answer is No.