The perception regarding WWI is that in the main theater there was little or no movement. If the game is true to life, you end up with a static bloodbath. If you get around that by making things move, it wouldn't be WWI.
That's because many people tend to equate the western front with WWI. The eastern front were never as static and the greater length of the front forced the defenders to spread out, thining their lines, offering better chances for break throughs. Becasuse of great distance it also made it harder for defenders to react once a breakthrough was made. It sheer size of the eastern front compared to the western front also allowed more maneuvrability in general.
For an interesting board game of this period I can recommend The Cossacks Are Coming!:
http://www.boardgamegeek.com/boardgame/11241/the-cossacks-are-coming
http://www.boardgamegeek.com/boardgame/11993/the-cossacks-are-coming-2nd-edition