Re: More Main Categories on one Wiki
I am not sure that I completely follow you, but it looks like you are interested in a multitiki. See OneTiki-OR-ManyTikis and MultiTiki19 for a discussion. If you want to share data (usere, galleries, permissions) across multiple tikis, then this is exactly what a multitiki will provide. You can have single-sign-on across them. Because the galleries are shared, the search spans the multiple tikis.
gary