Iliana - I think your issues are quite common for many site owners - I would like to see a system where we could give mods greater control over just their forum - including banning people from their forum.
Ultimately I would like to give groups (guild masters in your case) their own forum, which is linked membership wise to the main forum - but in which they control many features including headers, footers, portal settings, who can and can't see the forums etc..... whilst at the same time having joint forums with the main site.
If we do not have groups like this within the forum site, all that happens is that the groups break off, and set up a rival site just for them - helping to destroy the community. This might sound good for a forum company as it means more sales - but in reality it doesn't - these groups often will use a free stand alone system (phpbb for example) or use a free hosted service (which is precisely what we should be able to offer them!!!)