is there a plugin which can activate/unlock content?

Hi:
I have two versions of a website, one “basic”, and one “full-featured”. I want to launch with “basic”, then at a given point, have the ability to ‘flick a switch’ and turn on “full-featured”. Is there a plugin that can do this? My search didn’t turn anything up.

They would each use the same theme, the only difference would be which pages are visible, which widgets are on, and perhaps which custom options are enabled.

Thanks a lot for your ideas. If I can’t find anything I’ve considered developing two separate themes/databases. Regards,
-JP