I'll try to be brief and realistic:
For proper sniper concealment, a few criteria would have to be met:
open terrain:
The ghillie suit base is great, but ideally there would be a button which, when activated, caused the soldier to "veg up" incrementally. Holding the button would essentially delete a portion of whatever foliage was around the soldier and add it (in a predetermined, character model already created) to the ghillie suit. Perhaps five increments. Hold down a button for 5 seconds, there are small yellow daffodils deleted from the terrain and the soldier has a few on him. Five seconds more, and now the character model has a few more.
The vegetation must be able to be "burned through" or focused past. When near a pocket of grass for example, the keyhole effect would cause you to still be able to see pretty well through the grass, while making you much more difficult to detect. Clippers to delete small amounts of vegetation to create loopholes would also help.
draw distance: there is no point in hiding in grass if your opponent's computer never renders it. Given that the human eye can only perceive so much detail at a given range, I think it would be fair to have a prone soldier show up as a nearly indistinguishable dot amongst the countryside when viewed through the naked eye at range. When scoped in, let's render all aspects of the terrain simultaneously. I admit I am not familiar with exactly how the game engine does this, so just take it as a basic idea of what needs to be accomplished for proper concealment simulation.
Indoors:
If we could have a netting that could be placed on windows to darken the inside, that would be ideal. Perhaps in conjunction with a dark blanket for the backdrop. This will mostly come down to lighting, and the acknowledgement that this is a simulator, and as scarey and unfair as it is, a properly concealed sniper in the rear of a dark room, is, for all intents and purposes, invisible. If you think he is there, hit it with a tank shell, but you will never see him. Or if you do see something, you will never be sure it's a rifleman.
Sufficiently busy interiors (furniture, etc), maybe curtains or blinds (that can be interacted with to shift in maybe 3 positions?), would also help.
Can we get some tall office buildings with a lot of windows? Huge target, I know, but they would be fun to assault, shoot from, and ultimately blow up with airstrikes.
Quickly off topic; I hope I will be able to use track ir5 to change positions similar to lean left and right in arma 2. I would love to be peeking left right, up down and all around while playing.
Thank you