I will start out by saying I enjoy TES combat and always have and I personally feel it has consistently gotten better but like with anything in life there is always room for improvement and I had a concept of how that might be done in future TES. Bare in mind this is a base concept and can obviously be improved upon. Also I am trying to keep this short so much of it is simplified and I encourage you to read it fully before commenting in anyway.

The concept is quite simply based on the limitation of limited buttons and keeping things simple yet complex in a way that allows players to truly master the different fields of combat.

0) The idea is to allow a more versatile button system. In this concept consider your base controls (example xbox controller) the layout being default you have a button to draw your equipped weapon or spell and to interact with the world in all the ways. I say create a change up button which puts you into combat stance which alters the controls for strictly combat with the weapons equipped. Likewise there is a spell mode than a button can revert you back to exploration mode at any time.

1) In exploration mode the buttons would be extremely similar to what they are now. A key for this menu a key for that menu a key for interacting etc.

2) Melee combat mode : Once activated your weapons are drawn and the layout changes. Like normal you have triggers to attack and block and holding allows power attacks. Now the bumpers could be used for other attacks like shield bashing or swinging your weapon wide for an attack that wouldn't hit hard but would encourage your adversaries to step back. (These are strictly examples) Other buttons could be set to throw out a torch in your off hand or simply to change weapon sets on the fly.

2a) Archery mode : I don't really know how to add more buttons to archery as it is a simpler concept but I would consider a button to draw a second arrow or to use a torch to light one on fire etc.

4)Magic mode: I have thought most thoroughly in this section as I have never enjoyed magic as much as the other styles of combat so... For when you are in this mode there should be two buttons that allow you swap from specific spell fields. By spell fields I mean instead of learning every fire, lightning, frost spell you'd learn the field of element and instead of equipping any individual spell you equip the "field".

Let us assume you select Fire spell field this will alter your buttons to all cast fire spells making the magic much quicker and allowing you to quickly use the appropriate spell for the appropriate situation.

-Left trigger cast your cone spell. Right trigger cast the quick ranged spell. Charging right trigger casts the stronger ranged spell (aoe fireball or chain lightning etc). Left bumper is now used to cloak yourself in fire right bumper allows for additional mana to be used by holding it down you add effects to any spell cast.

-Instead of learning spells you get those simply by leveling up the field of magic and tomes are now used based on your skill level to add effects to your spells or perhaps even simply change the way they look. This can enhance individuality while playing the game and gives players choices that are not permanent but can dramatically change how they fight. Master spell tomes for example could add effects that effect the entire school of magic.

Anyways Feel free to add to it and if people like my idea I will post a more detailed one that I will put more time into. Hope you found it interesting!