Codes aside, you should check with the utility to find out about the composition of their gas and its effect on the copper. I'd prefer to have the drain and water supply lines come up through the floor and the pedestal instead of the wall for a better appearance. My home is on a crawl space on is a one story ranch style house. There are polished brass tail pieces and traps for open plumbing. Not by code.
Enforcement is up to the local agency.
You have to check with them.