It would be nice if you could add support/functionality for STIX/TAXII services.
This would allow an an extra layer of security, blocking malicious sources globally recognized also by other products.
In general, most of the STIX type lists are already incorporated into our services like Botnet, and other features inside of TDR.
For custom lists, there's currently a feature request open -- FBX-17962. This is for External Dynamic List (EDLs).
Please create a support case if you'd like to follow that request -- just mention FBX-17962 somewhere in it.
WatchGuard Customer Support