Three position camera control

Im operating UAV plane, controlled by Pixhawk for aerial imagery purpose. Pixhawk is controlling camera shutter by one channel. But this camera control has just two positions - shutter pushed and shutter released. Would it be possible to control camera by three positions command? I mean following positions: Lens closed, Lens open/shutter released, Shutter pushed. It would be great to have a possibility to close lens before landing (and during take-off) and Canon camera with CHDK can do it easy. Now I have to control these three statuses by two channels, but why not to control three positions by just one channel? Does it exist such a functionality in current arduplane software or is there, at least, any not complicated way how to customize it?