I’d like to discuss the idea of modding diablo 3. Regardless of this never happening (and regardless of modding skills required) - let us talk about hypothetical diablo 3 mods / cheats/ insane builds - just for fun.
-First thing i’d try, would be wearing all 4 Wiz-Class sets at once.
I’d add all the D2 areas for additional gameplay and change the story to make it interesting. You know make it 10 acts with a new story interconnecting all of them.
OP, modding your own D3 is beyond hypothetical today, just saying.
For obvious reasons i won’t expand on it.
Remove GRs and Paragon 2.0
Add dungeons with multiple bosses instead of thousands of mobs designed to be multi-shotted
Skill trees: reduce power to every single skill down to 50% of it’s current version and add up to 5 levels to each one of them (something like 50%, 65%, 80%, 100%, 125%)
Incorporate passives in the “skill tree” process in some way like make each Passives take 5 skill points so some people would upgrade more skills if they prefer but others would just play with like 6-7 pasives at a time if need be
REMOVE critical modifier from everything that’s not a glove or weapon and give the jewelry some kind of secondary bonuses not necessarily related to damage
Add in more difficulty levels, more bosses, more legendary gems, add in new legendaries and sets etc
Remove paragon levels entirely
I would make a really nice Not the Cow Level with higher frames cows. 8 bits sounds cow saying mooohhh… Would make them 2-3x harder to kill and to double their exp.
And i would add more 100% cows density with cow lancer mobs. So players would die. I like to die not to melt stuff.
Make Vanishing Dye actually do what it warns - work on the underwear. 
Haha. there’s a mod for this in Skyrim 
Nerf all the insane set/leg bonuses to where 50% would be a godlike buff and remove 99% of all the difficulty settings.
Set up some ReShade presets so people could have a D3 closer to what they expected it to look like. Me, I like what is there now, but I know lots of others would prefer a darker setting, something ReShade can provide.
Big nerf to legendary and set items. Redo stat system. Get rid of cutscenes in boss fights.
OH man. Where to begin.
New monsters.
Custom campaign.
New followers.
New legendaries.
Rework some old legendaries.
Bring back frozen orb.
Tweak exp rates.
Make more paragon additions.
Entirely new sets based on new custom campaign.
New classes.
A difficulty overhaul for sure.
More goblins! More pets!
Make all items able to be upgraded and formed into your perfect dream item. Only requires time and mats! 
Time to open back up AFJ and poke into d2 again.
i would try to influence the devs first;
-then maybe a system of authorised modding.
-mods should never influence Lore and complexity.
I’d make a druid. And maybe expand the inventory. Make stash mobile.
then i want;
nudity in art and statues, nude succubi and satanism Lore scenario’s.
visible heads chopped off while mobblasting.
all SINS of HELL.
all torture techniques through human history, for me to see, hear and punish.
yeah, that would relax me fine. 
yesss 
Maybe blizzard could to create custom mode where a new character should be created to play in this mode. So custom mode character just can play in this kind of game. So blizzard could to copy Ark Survival Evolved where they elect the best custom map and add to official server.
What would I do if I could mod Diablo 3? Nothing. Nothing at all. Modding the game would ruin it. It’s not an ‘rpg’ in a comparative model to things like baldurs gate or Fallout.
Anyone who has ever played open battlenet Diablo2 would understand. You just dont mod Diablo. ^^
Cheers,
Happy holidays!!!