Yah L7 would be prefered, especially OpenDPI from http://www.opendpi.org, by iPoque. They have DPI appliances that use DPI to traffic shape, and have released by open source their DPI engine.
It has flash, youtube, and bunch of other L7 patterns based on pcap files rather than headers that L7 uses for their open source engine. A netfilter wrapper has been created for it. I’m trying to figure out how to install it into Zeroshell for better shaping.
I am working on L7 filter patterns for flv and custom ones as well too.