There are many things I would like to see in TES VI, but in this post I will focus on one aspect. Character Stats.
Perks:
The perk system of Skyrim is good in theory, but it ultimately curtailed the whole system. By having a majority of the perks perform simple magnitude increases and cost reductions, the whole purpose of skill values is marginalized.
Increasing your stat and then allocating a point to unlock more of what is inherently given is profoundly insulting. The perks themselves simply become "feat taxes" (term for those familiar with Dungeons and Dragons). There is unlikely any reason that the incremental increases couldn't be factored into normal skill-value computations. Other than to artificially fill-up the perk trees, I can't see why Bethesda went the route they did. What could have been handled entirely within the skill value itself has been relegated to manual management, defeating the entire goal of simply "becoming what you play".
Quantity is good, but not at the expense of butchering what you already have. It's like cutting a pie in half and saying that you now have two pies, instead of owning up to the fact that you still have one pie (and an ugly butchered one at that).
Attributes:
I feel that Bethesda threw out the baby with the bathwater on this one. I agree that the old attribute system rewarded meta-gaming over roleplaying, but the attributes themselves served a purpose. Attributes were a foundation of interconnected cogs driving mechanics that gave "character" to the overall ability of your virtual adventurer. Being able to improve your performance in all strength based activities across the board through somewhat unrelated skills is a natural progression system in and of itself.
For example: Someone that does crossfit will perform better at basketball for the first time when compared to a sedentary person of comparable skill in the sport. Attributes are like aptitudes, which is different but foundational to skills.
I believe the best solution would have been to discard the incremental increase of attributes at level-up. They could then give each attribute its own experience bar letting it increase fluidly like the skills; this would effectively eliminate the dilemma of meta-gaming skill-ups per level. Your warrior gets stronger swinging his sword, the mage becomes willful casting his spells, and the rogue becomes more agile darting about.
You could even tie-in attribute requirements for some perks, as long as they are not arbitrary magnitude buffs. Any magnitude buffs from an attribute should be handled like it was in Morrowind, where it inherently scales the output.
You don't even need to have the character manage it. Just let attributes take care of themselves like skills, improving as you use it.
Skills:
I can see why Bethesda keeps reducing the number of total skills, but the line has to be drawn somewhere... God help us all if they announce for TES VI that there are only 3 skills; Combat, Stealth, and Magic. I actually wouldn't be surprised if they did; it already looks like they slashed skills from Fallout 4 completely. If you make another elderscrolls game, please Bethesda, do NOT do this!
If they could manage the animations to correlate with them, I would like to see the return of hit chance and spell failure. I think people might appreciate this mechanic if they actually SEE their character struggle to hit their enemies when outclassed; and imagine their reaction if they see their own character dodge/parry swords and dodge/resist spells.
Health, Stamina, Magicka:
I actually thought Skyrim did this just fine. I always saw the Health bar as more of a luck-margin anyway; once it runs out, the next sword swing connects in a fatal way. The fact that these stats regenerated continuously is not a bad thing. If you want to simulate health, stamina, and magicka perfectly, then you would need to get into mechanics such as those found in "survival" mods. It would be cool if TES VI comes stock with its own optional survival settings, but I would rather that they bring back attributes and more skills than focus on that.
On a side note: I would like to see a limit placed on the number of potions a character can consume within an in-game day. It seems rather absurd to be able to chug down 5-10 potions mid-combat, the metabolism of any person would be overloaded within the first few, depending the ounces consumed. I never use them, because they seem like cheap "I-WIN" buttons. They are, more or less, as useful to me as the in-game food when it comes to entertainment value.