It'd be awesome to have access to more external controls, but Microsoft won't allow this due to their UI guidelines. Think of it this way, what if someone were out shooting photos while listening to music, how would they adjust the volume?
(ahh that just brought back some rosy memories of my first digital camera, the
Casio EX-M1. I thought I was living in the future...)
Coming in the next update
I haven't added support for the FFC yet. During early testing I noticed quite a few bugs with them on different devices, so I decided to focus on the main camera first. FFC support will be coming later down the line.