Touch/Gestures would allow the end-user to control pan, zoom, and rotate on touch capable devices, such as the Wacom Cintiq. Most 2D and 3D apps support Touch in some form or fashion and those of us that use a touch enabled device are accustomed to working with it.
Justification
Having Touch available allows the end-user to work fluidly and seamlessly on such devices using one hand to paint and another to pan/zoom/translate, making production easy and fast. When painting, it is important to keep your eyes on your work. With Touch enabled, it makes it very simple to paint all around an object using the stylus while simultaneously rotating it with the other hand, for example. This is much nicer than paint, move stylus to somewhere off the model, rotate via stylus, move stylus back to model and continue painting, etc.
Implementation Details
Touch should be implemented as it is on most touch enabled devices so that standard gestures control pan, zoom, and rotate - a single finger rotates the object, ‘pinching’ two fingers zooms in (the opposite zooms out), two-finger swipe to move/translate. Palm rejection should also be implemented in order to reduce the possibility of accidently painting on the scene object with your fingers (i.e. only the stylus’ input should be accepted for painting input).