I'm sorry but everything you just described is not a PM's job. The PM does NOT represent the customer. The PM is responsible for delivering an agreed upon set of functionality within time and budget.
You're describing a product owner.
edit: typo
You're describing a product owner.
edit: typo
[1] http://blogs.msdn.com/b/techtalk/archive/2005/12/16/504872.a... [2] http://microsoftjobsblog.com/zen-of-pm/