They simulate this idea to a small degree already. The different abilities typically have a range, which would represent visual or sound distance (like the Team Leader's 'Situational Awareness' and 'Fire'). I suppose this could be taken even further, but I would be a little worried about complicating the game too much...
I know. That's exactly why I chose this game to post my thoughts although I've tried almost every tactical miniatures game that I could get my hands on. This game has a simple but very effective foundation to support even further complexity. Note that complex rules is a completely different thing than complicated rules....
Why be worried? Haven't we seen enough light to medium 'weight' tactical games already? Why shouldn't we take it to the next level and have a more complex one for a change?