I think you should be aware that replacing the internally routed hydraulic cable will be a time consuming job that is very unlikely to solve the squeaky brakes.

If the brakes work well, then try to overlook the squeak. It is common in disc brakes. Squeaking will have far more to do with the pads and the discs than anything else. As long as you are l not losing fluid, I would leave the rest of the hydraulic system alone.