WWI would've been great for the first Red Orchestra.
BEHOLD:
http://www.moddb.com/mods/grabenkrieg
I know about it, König, it's just they would have to make a heavy edit to the base gameplay for me to get into it. Things such as the return to the suppression system that DH has rather than the "everything is zoned in and deaf" system that RO2 has. Not only that, but heavily increase the weapon sway of unsupported weapons and get rid of the laser accuracy of all of the weapons. RO2 in its current state is much too arcadey for WWI or even WWII, since you just have idiots running around with prototype assault rifles that never saw Stalingrad to begin with.
The beauty of RO1 is if you're crossing open ground at 100-200 meters away, you have a pretty good chance at surviving. There are excellent marksmen in the game and I'd like to consider myself one of them, so you'd still have people picked off if you weren't making good use of micro-terrain or cover.
I have two in-game examples of the rediculous lethality of RO2 vs. RO1:
The map "Fallen Heroes" in RO2 is a remake of "Fallen Fighters" in RO1. In FF I can move from the rear areas of my respective base capture point towards the center and even make movements within the center without too much trouble. Most of the fire I'll take will either be flanking fire, artillery, or the machine-gun of a tank. However, in FH, if you're not moving without the aid of smoke or safety in numbers, you'll be sniped from everywhere and anywhere since everyone is laser accurate.
As I've already let everyone in the FKI know, I do (or rather did until RO:Ostfront and Darkest Hour died because of the server glitch) historical realism gaming with a unit. (We've since moved to Invasion '44 for ArmA II) However, we had just come from preparing for RO2 by playing Red Orchestra: Ostfront and we were at the top of our game, just getting out of a Battle of Berlin campaign with a multitude of other units also preparing for RO2. We were extremely efficient and deadly, tearing everyone to shreds even each other during trainings. (Dom Pavlova still gives me nightmares, haha!) However, the most suitable map for our realism type gaming was "Red October Factory" with the amount of differential terrain and room to maneuver compared to many other maps. However, no matter how well in cover or hidden defenders would be or how far back we'd have the attacker's starting point would be, we'd keep on running into cross-map sniping or attackers being able to ignore suppression and pick off machinegunners or riflemen in good positions... positions that would've been much more difficult to neutralize in RO1. Trainings would be over in a matter of minutes with the same result each time... 2-3 guys on each team skulking around to get the drop on each other and kill the last enemies.
I emotionally invested myself into RO2 and really tried to like it and forgive its downfalls, being very optimistic about features being fixed. However, even now, most of them still haven't been fixed or they've just been shirked off. Not to mention the terrible tanking. All of the realism units that did play RO2 abandoned ship about 3-4 months afterwards until it was us and one other unit. They moved back to DH and so did we. I don't know if I can ever look back, unless some mod would fix the terrible issues brought on by the TWI team.
TL;DR: I'm skeptical.
/rant