I suggest being able to stack and break down runes and gems, would be a huge space saver.
Guess we just going to have to do what we always have done, make a mule for gems and make a mule for runes.
Yes but purists like being purists
When I play D2 with my duo, they dudn’t even bother picking up grand charms, large charms, certain jewels and gems. Thats the system working as intended, those that want to organize and compromise get rewarded.
Break down runes? For what? To break Cham into 2x Jahs? and 2 Jahs into 4 Bers ? 
:D:D :D: D:D :D:
P.S. : Would you trade me Zod for 3 Bers? - What? NO! You know I can break it down to 8 Bers ?
Lets wait and see. We might get a future update for this. I vouch for this and charm inventory.
I wouldn’t mind a 1:1 rune downgrade option.
Break the stack into individual pieces by cubing it.
No one will complain if they implement this and i am one of those the mod players call a purist
Just kidding of course, but I do not think stacking is the way to go. One of the fellow priv. mods already tested that and it turned out to be a dupe 50x Ber stacks fiesta… Id rather not
I would. Dont try to change the itemization balance of the game. And that is a differnt story to the OP.
If they are able to keep dupes clamped down, you might change your mind. 
You could also make a separate tab in the stash that hard stores them. By hard store I mean not as movable item but with an icon and a number next to the icon. If you insert a rune the number goes up. If you want to use a rune lift the rune icon up and the counter goes down by one for said rune.
Same with gems.
Once you can dupe, you can dupe all you want. If the ruens are stacked it just makes the process faster, but the dupe is still there. If the guy wants to do 100 duped hrs, he will do it by duping singles or stacked, in 5 minutes or in 20 minutes, but he will still be duping 100hrs.
Yep. So essentially all these good ideas we have already seen in private mods like Path of D. Just hire this dude who implemented it for his priv. mod and we like it after 15 years no one in blizz did
I’m not wanting any changes for at least a couple of ladders. Both to establish a good control benchmark, and to determine what the hackers are doing.
Duh? But what exactly you would be doing for couple of ladders? The same as the previous 20 ladders in Vanilla?
I also dont need this, but it wouldnt hut the game.
Yes.
Sounds fine to me. 
Keep in mind duping is not a process you can do anytime you like or choose to. If something allows duping to be sped up to oblivion it would be bad , very bad. Id rather duping taking 20 hours instead of 5 minutes.