Here's my thread from this recent repair:
second-to-last post shows the end result. I removed the regulator...there wasn't room for it, what with the bulk of those sharkbite fittings. Like I said in that thread, there is a shortage of lateral space with this configuration...
anyway, you can see the white plastic (pex) pipe, that replaced the copper riser.
the sharkbite fittings are what made it possible for me to do this, without removing the bathroom. Just snapped the pieces together, and slid it down the existing hole in the floor, with that riser dangling down. Then I went outside, cut the pipe to length, and snapped on the drop ear elbow, and screwed it onto the frame. (I did have to drill one little hole in the frame, as the new elbow had differently spaced screw holes from the old one. I never took a pic of the outside, because it looks pretty much just like the original config.
I think this is the only time I ever "fixed" something, and putting it back together was actually easier and faster than taking it apart.