New to CI - have small question...

[eluser]jedd[/eluser]
It'll certainly be bigger .. and, yeah, probably more interesting (for varying values of Interesting).

Are you sure you can't utilise Joomla or Drupal or Deki/Mindtouch and just bang in extra code for the additional things you need? Most of those have got a huge set of funky add-ins already, so you might find people have already got those products doing what you want.

Writing a CMS from scratch is a mammoth job, to be sure.

You might also want to, if you are set on writing a custom one, take something like [url="http://github.com/philsturgeon/pyrocms"]pyrocms[/url] and contributing plugins to that, to get where you want to go.