At a quick glance I’m quite sure bbPress could do everything that you mention above, just not out of the box will it do those things.
You would need to make these customizations yourself or hire a programmer to do them for you.
The ‘threaded “hierarchal tree-style” would just be a matter of making some custom templates and would be quite quick. To setup the different theme for different users I think there are a few WordPress plugins that let your users choose what theme they want to use, so have two themes, one with the default bbPress theme (with or without customizations, and the other theme with your customized “hierarchal tree-style” templates.
There are some docs on getting started with custom templates http://codex.bbpress.org/theme-compatibility/