I'm essentially against having the artificial crosshair system as mentioned, simply because they just didn't do it that way in those days- nowadays there are any number of gunnery systems available with slave sights and such, but not so in the Good Old Days.
And back in those days they didn't drive tank with five buttons and aim and shoot and such with a weird thing called mouse. Or if there's unwritten part about that in history I'd like to read it.
3) Introduce a Gunner's position, in addition to the existing crew positions. More realistic, and allows the TC to concentrate on managing the tank instead of multi-hatting as is presently done. Note that the Gunner position would be gunsight-only, with no external view (as is the current MG position).
Now this is not a 'bad' idea in case of realism, but let's see this:
Let's pretend we have about 32 - 40 player server. It takes four guys to man a tank. Practically that leaves only about three fully manned tanks (presuming if they do have all four positions). Now at bigger servers, let's say about 50 players, we could have about five fully manned tanks. Now it would be more realistic by the idea, but let's face the bigger problem:
It would not work 3\4 of time. Why? The problem of being a video game surrounded by weird inviduals. Some people might enjoy team tanking and co-ordination (which belongs in the minority), while majority is often just like "get outta mah tankzz0r!" or "omg noob learn to aim giev meh ze gunnarz."
Now let us put that in practical situation. Yes I know there are servers with good people around or players who truly want to co-ordinate, but the majority of people (based bit on both personal experience and amount of whining around the RO forums) are silly dillydallys who just rally their tank in front run'n gun style and jump back'n forth in turret-driver position and TANKRUSH KEKEKEKEKEKE!
So practically you would need people who really know each other in way or another to have fully manned tank idea to work. And in combined arms maps if we have like two tanks each side and both are fully manned, that's already eight people. Roughly a third of one side's people even at larger servers. I can imagine in Konigsplatz the poor Soviets where their tanks eat about 7 guys from their 26 (let's pretend we have 52 player server). That's almost the rough third of the entire Soviet side. And let's add the possibility that these tankers are so called idiots (aka n00bmastarz) and we have one big Kindergarten going. I know, this happens already, but usually it's just driver and gunner-commander in tank. Rarely some random people stick around in the bow-MG spot.
Alternate possibility is that the commander seat is left unused, but generally having four man tanks is bad idea. As realistic as it might be, it causes server handicap in the game itself. It's like if we implement a forced fear of death that your accuracy is suddenly decreased -80% and stamina is halved among with your speed and your vision looks like you are drunk.
In short: For practical reasons it is not good idea to add official seat for the commander. Sure for "realism" reasons, but I doubt why add such small realistic idea when the entire tank system needs a major overhaul to be even slightly realistic in the first place? Fixing things in the long runs would be more ideal, even though I doubt we ever get official updates in the armour system.
And as with the idea itself I fully offer my support.