PEX, so far as I’ve been able to determine, works well for it’s intended uses. From what I’ve read it is very inert and mechanically strong as a pipe material, and has many advantages, the main one being flexibility. If there are any problems with PEX plumbing, they seem to be that the plumber really has to understand the material, especially the joinery techniques. Being a conscientious plumber, I have studied the material and the techniques and even bought some of the stuff and experimented with it. However, I have not yet used it on any jobs…I’m probably just over-conservative, but I’ve been preferentially using copper for about a quarter century now for supply lines and I feel very comfortable with it. I’m sure there are cases, like the one you describe, where PEX might be more convenient to use to reroute pipes. On the other hand, rerouting copper pipe is really not that difficult, especially when you consider the flexible copper lines available.