Considering the age and popularity of the game, I'm surprised we haven't seen a solid boxed-set that includes alternate maps for different playercounts. I would expect the mechanics to work fine with any group large-enough for flowing alliances (5+) so it should be possible to design boards that work well with anywhere from 5-12 players.

The WW1-era setting of the game is interesting but really isn't essential.

But if course, this is exactly the kind of hardcore game that attracts hidebound players who scream bloody murder at things like alternate maps.