What's the most cost effective solution for repairing a slab leak?
The future health of the system can only be insured by gutting it. However, you're paying insurance; who cares? I don't really know the ins-and-outs of insurance but perhaps you should send them a letter recommending that they do replace the whole system; providing leverage for you to stand on when it breaks in the future and they want to raise your rate after you need to have more work done.

If you do care, then go with the third option after doing the second. Have as much work done, paid for by the insurance company, as possible. Piping into the attic should lower the bid to replace everything else. I wouldn't want to start tearing up concrete as a homeowner or as an installer, where I could just run it above (which your climate permits); much easier and less messy.


If you found this recent leak to be less than catastrophic, ride it out and let the insurance worry about it.
If it was, drop the cash on a new system and sleep better at night. 


Ideally you go big or go home (gut it). Otherwise however, I cannot quantify what your piece of mind is worth to you, and what possessions are at stake.

Bottom line: the most cost effective solution for you and the insurance company is to only repair what's necessary, provided you're not looking at a rate hike and don't have any Picasso's hanging on the walls.