Simultaneous mouse and controller input

I'm playing with a Steam controller and while the joystick emulation works ok, I feel it'd be a lot better with mouse support for the camera. Currently if you're using a gamepad you can't simultaneously use the mouse for camera control. Because what insane person would want to use a controller and a mouse at the same time?!

Well instead of a joystick the steam controller has a circular touchpad on the right that works pretty well for a lot of games that use a mouse. It'd be nice if I could use the analog stick combined with mouse input!