As Rock Chuck discussed the pressure balance shower valve is how I would go. Also Kolher, Delta, Moen, T&S Brass, etc. all have residential grade and commercial/premium grade. It is worth the extra expense to go with the good stuff, in my opinion.
Go to your local Ferguson Enterprises, there will be one near you in NC somewhere, and ask to speak to one of their inside salesmen and get him to show you the good stuff.
