Instead of just stagger immunity, I would make a blanket "control effect" immunity, that affects things like staggering, knockdown/unrelenting force type effects, fear, frenzy etc. Basically, have it grant immunity to the effect for 5x its duration, for both the player and enemies with increased resistance. For example, if you fear a bandit for 5 seconds, they become immune to all other control effects including reapplying fear while it is on them for the full 5 seconds, and upon termination they become immune to all control effects for 25 seconds, and are 40% harder to afflict with control effects. The resistance stacks until the 3rd time, after which they are fully immune. This effect resets slowly over time once battle is ended.

Change all skill/effect/armor/weapon/resistance value determination to be contested against enemy power and level, with dimishing returns. For example, 100 sneak at level 15, counts as less when trying to sneak against a level 20 target, drastically less if the target is level 20 and a "boss". The penalty would scale at a rate that makes 8 levels higher than the player the cutoff point, an enemy 9 levels higher being nigh impossible to defeat even with crazy equipment. This would give incentive to take enhancing type perks and to wear skill effectiveness gear. It would also make the more powerful smithed/enchanted equipment less disruptive to standard gameplay as it would be justified by the drastic power leap when facing something many times your level of power.

Change traps to deal a percentage of the player's maximum health with each hit, while dealing a static value to enemies.

Apply a damage cap for both the player and enemies. As such, for standard enemies, it is impossible for them to take more than 40% health from a single strike, and impossible for them to deal more than 40% damage to the player in a single strike. This rating will scale with the enemy's level and rank against the player. Against an enemy 9 levels above the player or more for example, it would be impossible for the enemy to take more than 2% health in damage from a single strike, and it would be able to deal up to 95% of a player's health in one hit.

To complement no natural health regeneration, I would introduce a persistent status effect from rapidly squandering stamina, health or magicka. If you rapidly lose health, stamina, or magicka repeatedly, it can cause "persistent wound", "winded", or "enervation", these effects will have two stages each, with the second stage triggered by repeatedly triggering the conditions for the first stage. These would all be cured by a new type of special potion/item that cannot be crafted, or resting in a bed for a full 8 hours.

Persistent wound would cause health to slowly deplete, upon reaching the second stage, it decreases your maximum health by 20%, and reduces incoming healing from all sources by 50%.

Winded will cause stamina to fail to regenerate and makes you twice as easy to stagger, its second stage causes maximum stamina to slowly decrease with continued use until it reaches 0.

Enervation will causes your magicka to suddenly go into a negative value equal to the base magicka cost of the spell you cast that dropped you to such a low value, forcing you to wait an additional amount of time for your magicka to regenerate above 0. At the second stage, magicka stops naturally regenerating altogether.