What air filtration options exist for enclosures?
My residential materials expert referred me to these links (3D Printing Fume Extraction Solutions, and ABS 3d Printer Nanoparticle and Chemical Exhaust Air Filter) and thinks that you're pretty much on track with the idea of using activated carbon.

We both primarily print with ABS with my Replicator Dual and what's worked enough for me (in the past 5 years) is to keep my printer next to a window or vent in my den at home. The window is obviously a good ventilation option, but the variability that it creates in the ambient temperature screwed with my prints. Later, I moved my machine into its own hutch, which, if it is an option, would greatly help the overall environment for both the machine and any stored filament.

We'll keep poking around, but hopefully that helps in the mean time.