The mandate component is the lynchpin for the whole shebang. If it goes, very likely the whole program goes. Obama would then have to find new sources of funding it.
Remember, the goal is to eventually drive all private insurance companies out of business so the government approved plan will be the only alternative.
It really doesn't matter whether the government approved plan is actually set up and funded as a separate government agency or is a crony capitalist partner like AARP. All that matters is the top-down control.
Just watch.