This is not so much a design of TES6 as it is a rant on Skyrim.
Combat:
If you are going to have action combat for fuck's sake implement proper stamina system like in Dark Souls. Heck you can even do something interesting like Nioh with the ki system. Instantly guzzling down potions is not a fucking proper stamina system. Potions should only affect your stamina recharge rate. Also no more instantaneous eating and drinking, it should be interpretable.
Have attacks that do AoE damage from the start. Don't lock it behind a perk. Your AI and combat is not advanced enough to handle swarms of enemies well.
Implement proper fucking dodging mechanics.
If you are going to have flying fucking dragons or big ass ogres for fuck's sake implement a grab and climb mechanic like in Dragon's Dogma.
Implement proper stats and damage types for weapons, its shouldn't be just one overall number, have some proper trade-offs between weapons.
Same goes for your shitty armor.
Implement
proper AI, I hate to say this but you can actually get some interesting combat encounters if you properly set up some encounter templates with enemies having their own roles,
the magic system is that flexible. But that is only if the AI is competent enough. Add in more movement restricting spells like earth walls or fire pillars. Have the classic trinity setup
with tanks at the front and rangers at the back,healers healing and rogues flanking and backstabbing you in the shadows.
Quests and shit:
No seriously hire this guy:
https://www.youtube.com/playlist?list=PL-U2vBF9GrHGORYfnj6DOAFN1FgEzy9UA
He is singlehandedly doing the work you should have been doing with the civil war and factions and AI.
Have other adventurers that have the same drive to improve and get better gear that you can interact with and meet in quests that you can work together or be hired by the other side as your enemies. They can be also much more powerful then you and wipe the floor with you if you don't do your research on where they are and stumble upon them in quests. You also wouldn't be the only fucking thief in the world that can steal shit, in other words they can steal your shit and you can hunt them down and capture them like a bounty hunter. They can also be your companions.
Have at least a party of 2 companions with the maximum of 2. Be able to command them. They should not die in battle if you are still living. With this you can have quests that can have more complex requirements.
With this you can also have more demanding dungeons.
About leveling, the perk system was decent enough but implement some actual costs, don't make lockpicking free.
No more level scaling. Implement zones with their own list of enemies and power. For the factions their forces can improve just like you improve in the game over time. They should also have their top level powerhouses and you should only be able to face them at endgame. If you want to fight them you can only fight the encampments of the appropriate power level to you, or fight in a raid of another faction and be on the sidelines.
Run the fuck away. If you see a powerful monster or enemy encounter in a zone you can just run the fuck away and detour around. Similarly if you are too powerful the enemies can just fuck away when they see you. If the raid that you joined had all their forces decimated you can just run the fuck away. If your companions got knocked out in the fight while you run away they can be captured and you will have to eventually rescue them. If you have LoversLab installed some other things could happen to your companions.
For the next setting in the world you can continue the storyline where Skyrim left off and bring genocide on the elves. Maybe this time you are going to get things right with the whole war and factions and shit.
Hopefully the mods should eventually fix everything with how Skyrim keeps being constantly rereleased.
Why make a new game when you can just make the community make it?