If we have WW2 and CW, why not adding WW1??
With tanks like Saint Chamond, A7V, Renault FT, Schneider CA1 and the Mark family, WW1 mode would provide a really different gameplay with trench fights, possibility of mechanic fails, slow heavy tanks that have almost no gun rotation, multiple usable secondary machine guns, dynamic terrain, possible PvE games that resemble real battles and much more!!