I propose to take the great work that @luceos has done in implementing a feature (initially to protect discuss.flarum.org), but also releasing it to the public, as the next step for anti-spam. As written by @IanM in the newly created extension (https://discuss.flarum.org/d/33698-friendsofflarum-anti-spam) integration of the features of spam-prevention (https://discuss.flarum.org/d/31524-spam-prevention) into anti-spam could be a next big feature.
Spam-prevention currently offers advanced possibilities to put people into a moderation queue so that spam content does not get published. The current extension does not offer any UI elements making harder for novice administrators to configure the extension to their communities specific needs. Now that fof/anti-spam is available such nice UI could be built while integrating the features of spam-prevention. I hope that this also is in the intention of @luceos (who is not fond of building UIs 🙂).