How to Moderate First Blog Posts

Hiya! Quick question...

Is there any network setting or plugin available for moderating the first post published on all member sites?

We use Anti-Splog, and it works well for stopping bots. But we have recently had various spam blogs created by new users who publish very spammy posts. We delete these as quickly as possible, however, all posts on our network get auto-shared to our Facebook page and Twitter feed, which gets rather embarrassing when our followers think the spam is coming from us!

So, I'm looking for a way to maintain our free blogs, but require all first posts to be approved by the super-admin. Does anyone know of any existing Multisite plugin that would implement such a notification and moderation process?

Our SimplePress forums include a "moderation queue" which allows admins to moderate the first forum post from any new member. Once approved, all future forum posts from that user do not require moderation. I'm looking for similar functionality for blog posts on all member sites.

Please consider this a feature request, if no such tool exists!

Thank you in advance for any recommendations.