It would be nice if DPI could be set differently for horizontal and vertical movement, as an action and in profile settings.

Some FPS games allow you to configure different sensitivity planes in settings for scoped/unscoped aim, but most of the games lack such detail. I prefer having a lower DPI while holding RMB, but only for horizontal plane, since vertical controls most of the recoil. 

While we are on topic of DPI and sensitivity, OS sensitivity slider might also be a good addition for profile settings for all-in-one accessibility.
See cooler master solution for both as example: