It's not really a CMS either, I thing The Que is talking Application Server here.
IMO we will be over aiming if we do that.
We can provide the basics for building a site but IMO we shouldn't aim at creating a complete application framework.
It's nice to have reusable modules (like we already have in a way) but IMO we will make things a LOT more complex (and slower) if we start breaking everything apart.
My guess is that phpBB2 will become a bit more modular (maybe in part because of the Portal) but that's as far as we should go
We can provide some basic services as templates, plugin system, search engine, authentification, userbase, etc but we should keep it aimed at the forum..
It's a good idea that you have but IMO we should try to stick to our core business