Sitewide Tag Management for all blogs

Hello

I've just started to look at WP MU for use in our blogging systems.

We going to have about 40+ blogs running on the MU all chemistry related.

I'm trying to find a plugin that will allow me to configure a pre-defined set of tags and then push these out to all the other blogs.

I have found several excellent plugins that allow me to aggreate existing tags onto a page but no plugins that allow any management of the tags across all your blogs.

Has anyone seen this?

Thanks

Doug