I loved Battlefield 1 as much as the next guy, but there were things that EA and Dice could have done differently.
The melee weapons were one of my favorite features in BF1, and i was so excited when i unlocked all the puzzle pieces for one. But what if you could create a custom trench club? In WW1, soldiers crafted bludgeon tools using the things around them. They would take a piece of wood and hammer in pieces of scrap metal. What if you could do that in game? You would unlock the wood pieces or metal bits via. the battle packs, and there would be a crafting bench in the customize soldier menu.
On the topic of melee weapons, what if there were multiple melee animations for each location you attacked an enemy. For example, there would be 3 random animations that would be triggered if you attacked an enemy in front of them with a shovel. And this goes with all battlefield games, add a fist melee weapon. you could just punch your enemy to death! That would be cool!
EA and Dice also lacked in the soldier appearance customization in BF1. It would be great if there were early war and late war uniforms for each faction. And have multiple skins for each class, like 5 different skins for the German support class. It would a lot of work to customize different uniforms for each faction's class, but i think that it would be worth it in the end.
Personally, I think it would be cool if there was a gamemode called Trench Raid. It would be a multiplayer gamemode, and in it you along with 64 other players on your team, would go over the top and attack the enemy trench. The other team (with 64 players) would defend their trench line, but they would not be able to go into No Man's Land. The load outs would be pre-made to be historically accurate. Yo are also one hit, and once you die, you are unable to respawn. If all attackers are killed, the first round will end, and a second one would be begin. If they loose, the attacking team may be reenforced with 1-4 Landships. Once the defending trench is overrun, the attackers will win, but if the attackers loose all 5 rounds, they loose. The attackers may also have friendly artillery raining down on the enemy positions. The defending team would have rifle men, and mounted machine guns. The attackers also have rifle men, and also portable machine gunners.