water line in basement wall (Freezing)

I am going through the concrete floor slab Friday in my basement bathroom to set up drain locations, The bathroom is located in the S/E corner which has two outside walls. I was always told never run waterlines on the outside walls.
My plumber came by yesterday and said if I frame the walls with 2X4's, insulate R12, than vapor barrier, it would be safe to run the water lines on the inside of the warm side of the V/B by notching out the 2x4, than hang drywall.

I 'm concerned that once i jackhammer for the drains that's it. I won't be able to change location of the shower. The shower is 76.5" tall and the shower head will be about 78". That will be way above the frost line, in fact it will be above ground level. Would this be wise (OK) or should I redesign the room so all water lines are on interior walls?? I want to do this ONCE! Is this a safe way to run waterlines. I need some quick advice from some pros or people that have plumbed in basement bathrooms in an area that gets very cold for months in the winter, I am in Northern Ontario, beside Minnesota Brrr.
Thanks
Dave

I have generally tried to design so that the shower valve is on an inside wall. That way, if you ever need to replace it, you can get to it from the other side of the wall. If you put it against concrete wall, you have to rip up the shower.

I don't do new houses these days, but when I did, I typically ran all my water lines about 4' from the outside wall - except, of course, for running to fixtures.

Herk said:

I have generally tried to design so that the shower valve is on an inside wall. That way, if you ever need to replace it, you can get to it from the other side of the wall. If you put it against concrete wall, you have to rip up the shower.

I don't do new houses these days, but when I did, I typically ran all my water lines about 4' from the outside wall - except, of course, for running to fixtures.

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I agree. Think about what the future will hold. Your pipes will leak one day and you will be pulling out everything. Try to install the pipes and valve in a will you can open easy later.

Thanks

Makes sense to me, I will re-design for access and plumb inside walls
Thanks kindly for reminding me about the future problems