Several have mentioned/asked for this so go ahead and request.
I use a lot of MAC filters and only workaround I've found is to create more WLANs each with a specific different MAC ACL assigned (limit of which was increased in 9.5/9.6 update to about 27 from about 8 - I think).
So could have circa 128x27 MACs now. Hmm.
Clumsy but it works.