I don't think that the mechanics of aiming/ranging/shooting necessarily need to change (it's good currently in that it's skill and experience based).
But... I would like to see a gauge or indicator on screen that lets you know the current elevation of your guns and/or estimated range of the shots. Shots would still have the same element of vertical dispersion, and it wouldn't necessarily help with aim, but at least you'd have something of a setting to gauge your next shot on (more than memory of where you aimed with the mouse last time).