Disclaimer:I haven't read any of these posts,but I assume some ideas are repeated as a matter of course.
As a dedicated single player,would love to see a stash accessable by all characters.
I have played through Diablo II many times to "vegas" it and hope to get a nice item or set that actually mattered to the character in question.I think in 50 or more runs throughs
I got maybe 5 useful green or unique items.While this option would still be there with the all character stash,the player would have 2 ways to play a great game,extending it's replayability.
(and of course I am aware there were hacks etc available that would do this in 2,I never sought to go around the TOS)
Possibly a shuffle/select music option(after having played through the game with music in the proper locations)Blizzard game music is simply the best.
A book or something similar in the frontend menu.Say you click an ancient tome and it opens to a list of your played heroes with either the highest first or by date,with maybe an option to sort.turn the page and see some overview details of that hero.Items like bosses killed,how many times etc.Possibly a treasure chest here(on main menu)would be the stash of 10-20 items of so.I would love something like that.
The best and final idea is already a Blizzard staple.Take the time to get the game right.
Don't take too long though I don't think I can handle the stress ;).