the main criticism against Battlefield 1, is that it's not historically accurate and that it lacks weapons. The way DICE can address this is by:
 1) Adding a mode called trench warfare, for all the people who are more into the historical aspect of it. 64 vs 64, or 32 vs 32, no respawns, only bolt-action and semi-automatic rifles. Or let people rent their own servers so they could do it themselves. A perfect map for this would be Saint Quentin Scar. This would be more accurate to what WWI was like, and thus satisfying the critics. 
2) If the added all the countries in a DLC, or multiple dlc's that were left out, such as: France, Russia, Italy, Austria-Hungary and Bulgaria. By adding these countries, they could add the weapons that they also used, thus adding more weapons to unlock, and adding a more historically accurate WWI game.
 This would take a while, and probably multiple DLC's, but it would definitely make the game a better experience for EVERYONE!