The rough-in valve for the Delta Shower control can be ordered with shutoffs. Many plumbers order the standard valve and just shut off the entire home if needed. They tend to go at least ten years before any servicing would need to be done.
Every plumbing fixture needs a vent. You can tie those vents together at 42" above the floor. Being on Septic or Sewer is the same difference. It's all going downhill.
Here is a nice link to Bert Polk's plumbing tips