it looks like that is a closet behind the wall , correct???
flip the faucet to the left side and the drain vent over to the
left side adonw in the crawl space and that would solve your problems...
then all you got to do is take outhte wall and put in probably a 48
inch showeer stall...
I would definitely flip that faucet to the left wall or you
will be haveing to straddle the toilet every time
you attempt to turn on the shower.. th;a;t aint fun for big people