I also sent feedback to Apple a couple of times to get a seperate shortcut for Audio-only transitions, and I also asked them that if you Expand Video/Audio, it would get expanded for your complete timeline, even for clips you put in the timeline AFTER you expanded. That way you have to do much less clicking (now it works more like PRemiere Pro instead of FCP 7, and that was one of my biggest frustrations when I worked with Premiere at the time) then you should now.
There are also fade handles.
You know about the expanding Audio/Video? It's not the same as detaching, everything stays in sync, but you can make J and L cuts easily.
As I said, my only problem with it, is that if you expanded everything, every clip you put in the timeline after that command, is not-expanded again.