Visual fields of death, let's be tactical Options

[Wounded Ronin]

So, in lots of video games that are trying to handle firefights in a tactical manner, such as SEAL Team, the original Ghost Recon, and many others like it, an important gameplay consideration is which way your troops are facing. Basically, the game is set up so that if a NPC runs into the field of view of another NPC who is stationary visually covering a certain area or direction, the incoming NPC is likely to be killed by the stationary NPC. If a NPC is approached by another NPC while facing away from the approaching NPC, the approaching NPC is highly likely to kill the stationary NPC since he did not enter the stationary NPC's field of vision. Therefore, an important part of these games is often having your NPCs waiting and facing the right directions to be able to eliminate enemy NPCs who approach.

However, in many RPGs like Shadowrun, there aren't really specific rules for having a field of vision. There's perception tests, and TN modifiers to hear and see things, but it actually seems like the whole question of who gets to shoot whom first is mostly decided by the initiative roll. If I have wired III in SR3 or SR2 rules I will probably get to act first against any non-wired NPCs who approach me and the rules don't really deal explicitly with how to handle if the NPC runs up in front of me versus if he runs up behind me.

Does that make for a better or worse gameplay experience; does it detract from tactics in favor of number crunching? Is it possible or desirable or even realistic to have a "Ghost Recon Field of View" mechanic in a game if you wanted to be simulationistic? As a GM, how would you handle Wired Reflexes III versus normal goon based on whether the goon was approaching in front of the wired person or behind the wired person?