We have 100's of sub forums we would like to act as "separate" forums

[kh99]

If I understand you just want the main forum out of the breadcrumb? That's possible of course, but you'd need a plugin, or possibly you may need to edit code. There's usually a hook location right before a page template is rendered, so you maybe could write a small plugin to modify the value of the breadcrumb string before it's used.

I know this isn't the programming forum, but it's the best answer I know. If this sounds like the right solution but you're not a php programmer I might be able to help.