A mice doesn't have to be mounted, it isn't a storage device.
"Listening" to the USB port will probably require VBUS running all the time, thus wasting battery life.
The mouse issue is not a h-e-n issue, it doesn't belong here
A daemon could be made that listens to h-e-n's DBus signals and checks if a mouse is enumerated, but again, this isn't h-e-n's job.
The program itself is stable for what it does.