Round peg. Square hole.
You have general purpose tools like Joomla, PHPNuke, etc. if you want something that is integrated. If you want integrated, that is the best route to go. The only reason to choose WordPress or PHPbb over an integrated solution is because you want a best of breed tool, or something that is at least focused and thus more full featured in the desired area. So using a screwdriver to pound nails can be done but why would you want to.
Now, integration of best of breed tools is a different thing all together (or should I say different things all together
). There is a reason to do that in that you get the benefits of best of breed with a means of working between them. In that case the effort required is worth the payoff.