I remember WW1 arena in AW3. It was fun to goof around with when bored but it was never an arena you would get lost in. This is how it would probably end up for me here in AH2, fun to stop in every now and again but won't do anything for me. Wouldn't be worth the extensive development imo.
Although like m00t pointed out, if they have something already produced that just needs a little refining that won't cost them a boatload of man hours, then yeah WW1 would be a nice addition. But if it's gonna be a daunting project, then no probably not worth it in my eyes.