I have a working UI implementation via Scroll Rect which runs fine with the mouse in the editor. Is it at all possible to remap inputs so that the Gear VR touchpad works with that too?
Yep. All I did was forward the Vector2 of OVRInput.Axis2D.PrimaryTouchpad to the ScrollRect's velocity when you're hovering over it with whatever your hit testing system is, with some scaling and extra logic for direction and stuff of course.