which would be the recommended setup for the following scenario:

Two user groups will start with two separated forums or forum parts but same categories and are not allowed to see the other groups content. At a later point, both groups/forums will be merged and categories with two instances must be merged to one.

Which is the better way to handle this:

a) Set up two separated boards. Merge the boards to one -> how?

b) Have one board and allow viewing of the forum categories based on the group membership. Later allow viewing of all content and lock some of the categories.

Anyone with a clue?

Cheers!