Well there are a couple of ways. The outside being the last option.
With pex, there should be no leaks in the attic area if there are no fittings. When you make a home run from the manifold to the bathroom or other areas, make your fittings accessible in that area.
We have run pipes in the attic in insulated foam boxes. We have also run them in the top of the wall areas and created a soffit to cover the pipes, then run them down the wall to the fixtures. This is a little more sheetrock work in the end, but doable.
There is no easy solution, but getting rid of the PB garbage is a must...as you know.
Cutting and removing slab is hard...and the pipe becomes innaccesible, again.
I would rather know I have a leak, than something leaking under my slab creating huge issues later....much more than damaged sheetrock.