Small thing very much depends on someones personal preference.
I find the zoom in / out speeds in Arma 3 (RMB - NUM+) to be a little to aggressive. It is difficult for me to explain why/how i think this but i feel it zooms in so quickly that all i am able to focus on is the very center of the screen. (loose focus of surroundings / 'stuns' view whilst zooming)
I very much preferred the zoom in / out speeds back in Arma 2, where it was a little slower and did not 'stun' your view as much as in Arma 3 while it zoomed in.
Thus i would like to suggest an option gets added somewhere that would allow players to customize their 'Zoom Speed'. So that people who prefer it to be a little slower can set it that way, people that like it can keep it how it is and people that want it faster can also set it that way.
Hope this gets considered :)