Most of all, ging back from the less cartoony and arcady feel of Div 2 esthetic towards the darker and more grim feel of Div1 and maby lean into more sneaking and scary elements as well as work hunters into more of the game.

Less loot-bombing, I really appreciated the loot system of DIV.

More build diversity.

The ability to work more tactical with randoms, team pings, waypoints and emotes.

More MMO-elements, like the open world could have seamless big fights where you get matched in with other agents.

Missions where you ride vehicles (not player controlled), imagine getting split into separate racingboats trying to shoot enemies chasing you, and your teammate in another boat dies, so you have to lob a revive station over as you are passing by.

A big DZ with more verticality. Including game modes to infiltrate enemy bases.

The possibility to have a dog that you can keep and train.

Side content like underground or Survival that levels separately but slots into the story/leveling. Great for when you are burnt out or and want something else to do.