imagine dialog topics are structured like
folders in the sprites folder
topic
---->subtopic
---->subtopic
----->subsubtopic
this would help to create difficult dialogs and also
you dont have to think how many topics you must leave free
the structure of these topic system then allows you to make out the structure of the dialog more easily.
Yeah, that's a good idea - the current dialog system can get rather confusing once you've got a lot of topics. It's something I've been thinking about for a while, hopefully I'll get round to it at some point.