I'd go with a 3 panel design:
On the left, Nav. Controls the active panel. Do it as a 2-tier tree, so individual chat-rooms are children of the Chat entry, and your active Battle is a child of the Singleplayer or Multiplayer entry (and the option does not appear if you're not in a battle). So like:
-Me (unlocks, comm config, donate, profile)
-Browse (formerly Community, browses maps/replays/forum/missions)
-Chat (shows the chat-room browser)
In the middle, the active form or browser window.
On the right, notifications. A big scrollable space of every interactive
temporary thing going on. This would include downloads, battle-votes, and PM threads.