I don't see where you're getting this idea that there's no potential for retaliation. If there's no infantry between the archers and the enemy, it sounds like those archers are going to be in for a rough time when the enemy's turn comes around, especially now that the default move speed is 2. I'm no die-hard military buff, but the Civ 5 model strikes me as closer to archers' historical role than Civ 3 or 4 ever had: light units, vulnerable when the enemy closes with them, and best placed behind some sort of obstruction like a nice solid line of heavy infantry.
Well,
if there's no infantry between the archer and the enemy, then you're right. Otherwise, the archers will be able to sit there and lob arrows at the enemy until the cows come home and the archer is never actually risked in any way. This is similar to how artillery units worked in Civ3. You could just bombard the heck out of enemy positions without ever worrying about your artillery being killed. In Civ4, they changed this and the result was suicide catapults. Both models have their problems, but ranged attacks here will just lead to the same problem as Civ3 with the only difference being that the Archers won't even have to be adjacent to their targets to hit them.
Now, if archers worked exactly the same way as catapults, that would be a little odd. But to the best of my knowledge, this is not yet confirmed to be the case. And anyway, if you think about it, it's a little odd that archers work exactly the same way as infantry in Civ 4. I don't find it particularly upsetting for the abstraction to go one way instead of the other. As for unit redundancy, I see no reason at all to be so pessimistic (yet); catapults can be quantitatively very different than archers even if they work qualitatively the same. After all, swordsmen and horse archers work qualitatively the same in Civ 4, and no one is calling them redundant.
Well, you could be right. Maybe the bombardment strength of archers and catapults will vary depending on targets.
No, that would just again lead to a SOD.
Whoa! Don't back that up with reasons or anything!
The developers stated quite clearly that part of their reasoning for introducing this system was because they wanted to break up the monotony of sieges because currently, the best strategy for each side is to take the fight right to the city. For the defender, they need to mass as many troops as possible in the city so it doesn't get captured, and the attacker should simply bypass any defenders outside the city that don't pose a threat to the stack, and just start hammering away.
Reintroduce Zones of Control, however, and defenders can set up webs of defenses along an enemy border that will require the attacker to smash through the defender's front lines before being able to attack any of the cities.
So this addresses the issue of battles being fought outside cities, but I'll admit that it doesn't really address the SOD issue directly except that it compels defenders to spread their forces out more to hamper the enemy's movement through their territory. But the next idea combined with this one definitely would. For the attacker, ZoC would give them a reason to break off their army into smaller groups to protect the main column from a rear assault that would make it much more vulnerable.
How do you define the direction?
Units in Civ4 already have a facing direction. If they move west from one tile to the next, they're facing west. And if they were to be hit from the east, the attacker would get some kind of an advantage. One would also have to add the ability for units to be rotated without having to move from their current tile.
It's sure not realistic, that a
good supplied army will have penalties when they stack together

.
You pretty much summed up my counter-argument in your own. The more troops you have in one place, the more logistical problems they face and the more unwieldy they become. This was one of the reasons armies were typically broken up into smaller groups and moved over a wider territory when they went into winter quarters.
The disadvantage of some kind of penalty is offset by the advantage of simply having a much larger force in one place. The penalty does not mean that a large stack would be collectively weaker than a single enemy unit but rather that it would not be the invulnerable mass it can become in Civ4.
Hundred of miles? Create a map with a trillion of tiles, then you have an accurate scale

.
I'm sorry, but you can't criticize me for coming up with what you see as an unrealistic combat model and in the very next sentence say that I'm demanding too much realism.
If Archers can shoot units from two tiles away, then Musketmen, Riflemen, Infantry, Tanks, Artillery should be able to shoot three or more tiles away. In fact, if the developers are going to keep it consistent all combat should be ranged bombardment by the time these units come around. Units should not have to even get anywhere near each other to fight, and I should be able to kill all of a city's defenders without even having to be next to it. If you defend the Archers having this power, you must do so for every unit with a gun that comes after them because they have a considerably longer range than a bow and arrow. Because at that point, if you don't, you're not only saying you have no interest in being realistic, you have no interest in at least being consistent either.