BuddyPress.org

1) Not aware of any existing code that does this. However, your users would only have to go into their profile and change the ‘name’ field (this is what BuddyPress uses).

2) I think the addon you want is called “Plugin Commander.”

3) All of the core BuddyPress features are detailed on https://codex.buddypress.org/developer-docs/custom-buddypress-loops/ which you can use to integrate bits of functionality wherever you want. As far as third-party plugins goes, it is dependant on how the plugin author wrote their plugin.

4) Have you looked at new BP theme on http://testbp.org/? That and BP 1.2 should be released mid/late January.

5) Haven’t got time to discuss how to fix but look at trac.buddypress.org/ticket/1501