One, three, and seven are ones I could agree with. Two is a partial yes - having a to-do list would be nice, but having to fight a boss a hundred times over to optimize your character is just tedious busywork and not something I can support. I don't particularly care about multiplayer, though I suppose that the quest rewards and loot drama changes would make things better for those who do.
What I want to see make a come back most of all is the PlugY infinite personal and shared stash. Not having to worry about storage space was awesome, especially since I'm the type who hates to throw things away. If the devs are worried about duping, they could just restrict it to single player games, and restrict access to it when you're in multiplayer.
Stackable gems and runes (etc) would be cool, as would an autosort function and optionally an illusionist function - Grim Dawn seems to come up a lot, shows that it's quite polished and has a lot of good features - but I don't know if it would be feasible with the engine.
Another thing I'd like would be if GOG managed to convince Blizzard to publish D2 and LOD on their site, with mod support and cloud saves included, but I doubt that Blizzard would go for that, unfortunately.
More of a random thought, but I wonder if it would be possible to port Median to the remaster Blizzard is apparently working on.
...nah, probably not.