Layer 7 DPI? Feature request, I guess.
It's hard to really control traffic through the firewall without the most crucial bit, layer 7 DPI.
Any chance of seeing something like that in pfSense?
http://www.ntop.org/products/deep-packet-inspection/ndpi/ for instance, never really used it but it seems like it would make a great addition to the product.
Apparently there has been a feature request for it a while, also, I found while doing some searches.
I'm not personally capable of doing it but it would certainly improve my life a lot to have it.
ndpi is part of ntopng package. You can turn it on under Preferences > On-Disk Timeseries.