AppleTV should support pointing devices like mice and trackpads since it already support touch on a Siri remote
It seems like it would take very little additional programming to provide at least a base level support for pointing devices like trackpads and mice. The Apple TV is a very good device for streaming PCs using software like Moonlight. It already supports keyboards and controllers as well as Siri remote touchpad. It seems like it would be relatively feasible to support a trackpad or mouse.