"...If I were building a hose - or at least replumbing it - I'd put valves in that would allow me to run a mix of warm & cold water out through the hose. That way I could fashion an outdoor shower of some kind - plus it would provide warm water for washing dogs..."

That is why I always have a "utility" sink in the garage. With the right faucet set you can hook a regular garden hose on, and run hot/warm/cold water wherever you want...