![:S :S](/images/Smileys/wacko.gif)
I think, a nice landscape that makes you feel nice is very important, and to quote a famous hero: "I don't like sand."
As for other settings:
1) I think Battlefield 1 has shown that it is possible to pull off WW1 in an appealing way. The trick is to focus on late WW1.
2) A cold-war era game could actually be interesting, I think... especially when you consider that there was basically 2 Germanys on opposing sides, and both right on the potential frontlines. Relic likes to make german factions, so I say they should go for it. USA and USSR would be mandatory, of course. The ideological opposition of the 2 sides would also allow to give a clearly defined and interesting character and background to the armies. The iconic vibe of the cold-war era soviet army could attract an audience from russia when done right and can create a lot of atmosphere through the presence of rocket transporters as we know them form military parades.