Shower head on exterior wall – Insulation R-30 Rock Wool

We are currently building our home in the Utah area that is within 30 min of Salt Lake City. Our homebuilder recently decided to place the shower head in our shower facing the door – needless to say that wasn't going to work for us(don't really want to clean up a puddle every time we take a shower). So our only other option, according to them is to place the shower head on the exterior wall and keep the valve on the interior wall. The home builder claims that they discussed with the insulation company on how to properly insulate the shower head pipe. The insulation company told them that if they used an R-30 Rock Wool batt behind the pipe that it would be completely fine. So a couple of questions for the community:

1. Does this sounds like a reasonable fix(in an area that has below 0 temps)? is it normal to place a R-30 batt behind a shower head?
2. If you run a shower head line from an interior wall to an exterior wall(probably 3 ft run) do you loose pressure?