I have rescued kites twice and it is really difficult. I ended up grabbing a tip and dragging the downed mess to somewhere safe for the owners to retrieve.
The problem is that the downed kite is not going to sit there while you casually flip it over and ride away, and your kite and board are moving about while you're messing with the other kite and flying one-handed. The risk of getting tangled in the lines and bridles is huge.
I guess if you were planning to have to rescue kites (surfing in a group in an offshore) you could carry a spare leash with a quick release. Simply attach the leash to the pump leash and ride slowly away. You could release if it got too scary. Let me know if anyone tries this. I can't see me doing this anytime soon.
It has never happened to me but I have seen plenty of guys getting into trouble when rescuing boards when they don't know how to do it. Imagine how much harder it is to do with a kite.
One thing I found when rescuing a windsurfer (and all his gear) is that it is best to not try and plane away when you have a heavy load. It is much easier to partially sit in the water and drag and slowly tow the load to somewhere safe. Hands are not strong enough to hold against the power of the kite and leashes and stuff break when loaded.
Most offshore beaches are not worth the effort to kite from. Go and do something else. If I saw a wave that looked so good I could not resist, and the wind was good enough to give it a go, then I would go for it. If I lost a kite then that's just part of the price of kiting. It could just have easily been destroyed crashing it onto a stick or a shell on the beach.
PS. I would get a new friend if he lost his kite two sessions out of three ... and got grumpy at me because of his incompetence.