flow diverter for a nonstandard tub installation
Since the &quot;look&quot; is already rather &quot;industrial&quot; just put a 1/4 turn ball valve on the end of the pipe. Hole the same size as the pipe when open, shuts off fully when shut.

The picture implies that you could also possibly remove the blind cover from a hole in the tub to get a more direct path for a straight pipe stub that would take a normal tub spout, if you'd like a &quot;less industrial&quot; appearance.
Or replace the coupling and &quot;S-bend&quot; with two elbows and two straight nipples, which would allow the normal tub spout to screw onto the end of the second straight nipple.