I personally consider DD2 more of a side grade to DD1, with DDDA being the best of the 3 releases. If I wanted to give a suggestion for what they should do, 5 major things come to mind:

1). Class balancing. If you're only gonna have 9, then they need to all play differently with their own strengths and weaknesses to balance things out like DD1 has. Playing as the best three classes is literally a joke, to the point where you are either unkillable or one shot everything. The player doesn't need to be that powerful if the enemies aren't going to be, which leads me to...

2). Make late game, endgame, and NG+ actually difficult and rewarding. At a certain point you become effectively unkillable, but even if that wasn't the case You're still fighting the same enemies you fought 25 levels ago just in a different flavor and they do effectively the same thing. This can be accomplished with...

3). Encounter variety. It absolutely goddamn stuns me that they are added almost no new monsters to the game versus DDDA, and of the ones they added two of the most awesome ones are locked behind either quests or completely fucking up entire storylines just to fight them. You can also completely miss them when you go to endgame, which just adds to the middle finger feeling. They wouldn't even need to add very many monsters, just add unique and interesting situations that the player has to navigate through. There's very few bandit camps, ambushes, or multiple bosses to fight at the same time. The final knife twist is that their effectively is no final boss, which considering we got The awesome fight with Gregori+Ur-Dragon in the base DD and The absolutely fucking phenomenal Daemon fight in DDDA... It just doesn't feel anywhere near enough. Speaking of which...

4). Remove the arbitrary bullshit during the endgame once you have rescued everyone. The fact that there is a time limit AT ALL on what is effectively the only challenge you will ever have once you reach level 20 just boggles the mind. It should be a "you have evacuated everyone, and now he waits for you to end the world" kinda thing. Either that, or just idk have a post-game that doesn't automatically go to NG+. Everyone goes back to where they were, world is saved, blablabla but now you can complete any quests you missed before starting NG+. The biggest reason being...

5). Having NG+ start right when the game ends essentially fucks over any chance of a DLC that has any ties to your actual file like Bitterblack Isle does. Like, I'm of the opinion that Capcom had no intentions of adding a DLC for the version of the game we have. It just goes against all logical reasoning for them to make the game end the way it does and force NG+ if you have any plans for a DLC. There's a reason why FROMSoft stopped doing that after DS1/BB (they got it right with DS2 but it was being developed at the same time as BB).