TLDR: Animation where you pull the gun up to your face, hold rmb to aim(rather than click) and nicer graphics, possibly motion blur.
I'd like to suggest, if the developers are willing to, add a gun sight transition.
What is gun-sight transition?
Well, if you've played many or atleast one good FPS game, you would right click to look down your sights, right? Well if you notice, there is an animation where you'd pull your gun up to your eyes. Games such as battlefield and call of duty utilize this.
It makes the game look nicer and a much more advanced looking FPS. Despite the graphics, this game is an amazing FPS in its own way. I understand that it is in its early stages and that it will improve, but though my suggestion is not a major change, i think people would like it.
Then comes my next suggestion, hold rmb to aim down sights rather than clicking. In my opinion, people should be able to choose both, but an fps lover like me prefer to hold down the button so i wouldnt have to click once more to undo it.
Oh and one more suggestion, maybe a way to imrpove graphics? I could be wrong, the graphics may not be as good as they could because its in such an early stage of development, but yea, i think we could use a little eye candy. Maybe some more smoothening in the gameplay, i find it a little choppy at times because of the rough graphics. Maybe motion blur could be added too!
EDIT: Smoothening edges of the blocks to make them seem less rough and ridged. Maybe anti-aliasing? Oh and smoother gun aim, i notice the gun tends to flicker drag when you look around.
EDIT: OH and maybe make it so you can look down and see your body/feet like in ArmA or Battlefield :P