I understand your point Auge and you definitely know more than me in this matter

The idea of a thread based forum (MLF) combined with the ability for registered users to create Categories (like in Reddit) would suit my objective of creating a small Gaming Community, more Country/Language focused, without the need for Administrators come and create a new zone.

Lets say that the Gaming Community goes after 'MMO FPS/RTS/RPG', which in general have plenty of topics inside, this would allow registered users to open new/unexistent Game areas, like it happens in Reddit.
With this,

Instead of - http://mylittleforum.net/forum/index.php?mode=index&category=1
we would have - mylittleforum.net/forum/General/

An option that I would imagine is when clicking "New Topic", the Category pulldown menu, beside the current categories, would have an option to "Create New".

But like you said, would probably need a big change to the code and for own safety purposes I guess a minor security would have to be added so users wouldn't just add Categories without control.

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Maybe an alternative would be to add Custom Permalinks?