Sounds great! The way you explain the authentication method would lead me to think you'll be able to define the user profile database in the Poker server (ie "Profiles are called from com_user_profiles in the Joomla db. The field 'Name' is for names, 'md5_pw' for Passwords, and 'Chips' for chips etc"). Is that what you're implying? That'd be awesome, it would allow for an even greater customization!
Also a Web 2.0-esque installation process and admin backend would be amazing for the less tech savvy (or lazy, and who isn't lazy?) users (ie the way Wordpress is installed. Define titles, paths, databases etc. and hit Install, then log into an admin panel showing statistics and other data. Maybe even a plugin upload/install panel for third party plugins?).
Just my 2 cents! Posting anything that jumps into mind