If you want the PLAYER to see more of the map in one screen, then I fear the only way is to increase the game resolution. You'll find such a patch in the files section. Also see the FIFE project screenshots. If you want PC/NPC to see further, then I think that's hardcoded. I've been tinkering with the game's guts for more than 18 months now, and never saw anything concerning this.
Cheers.