Dave,
If the objective is to run experiments with some emulated wifi I could suggest
a workaround that we are using. It is not based on qdisc only.
It is based on ns3 emulation and linux bridges.
The radio emulation piece includes 802.11n and LTE.
For wifi you get the contention behaviour you're looking for and listen before talk etc.
You also get the TX or RX behaviour. There is also the propagation models from ns3 (fast/slow fading, etc. etc.).
The radio piece is a single Linux process so depending on the scaling you're looking for this tool
might or might not be useful.
In the repo, there is some documentation, but if you plan to use this stuff and need help let me know.
There is also a ML, in case it helps.
Luca