Interested in making a new campaign and some changes to the system to go along with it, but not sure what is possible. I've got some ideas from a brain storm session about what kinds of changes i would like to put into this mod, the basic theme is Soulsy combat and rouge elements.

CHANGES TO SYSTEM

1. 
   

   camera locked to 3rd person

   
   


2. 
   

   looking rotates camera around player

   
   


3. 
   

   player faces and moves whichever direction is pressed

   
   


4. 
   

   Locking onto enemies, strafing targeted enemy

   
   


5. 
   

   Rolling

   
   


6. 
   

   Climbing ledges

   
   


7. 
   

   All actions other than walking/jogging drain stamina, empty stamina cannot act other than walk/jog

   
   


8. 
   

   new attack animations, new attack hitboxes

   
   


9. 
   

   staggered eneimes enter cinematic kill vulnerable state

   
   


10. 
    

    "special meter" that fills up and grants powered up bonus time

    
    


11. 
    

    more eneimes on screen (more generic models?)

    
    


12. 
    

    perma-death, game saves on death and a new character must be created

    
    


13. 
    

    "tavern" area where x number of pre-created randomly generated characters are avalible to select which fall into certain classes. figther, rouge, mage. body types and certain facial parameters will fall into specific limitations by class (fighter are big, mages are thinner, rouges inbetween)

    
    


14. 
    

    New crafting system where enchanted items are created at time of item creation by having the correct plan, materials, and smith mastery

    
    


15. 
    

    cut-scenes either ingame or avi doesn't matter

    
    


16. 
    

    dismemberment in combat

    
    


17. 
    

    character leaves items on corpse at death, can be reclaimed

    
    


18. 
    

    adding new random encounters

    
    


19. 
    

    horse combat

    
    


20. 
    

    headshots on archery

    
    


21. 
    

    parry mechanic that put enemy into stunned state for repost

    
    


22. 
    

    new talent trees for classes

    
    

I want to figure out what is possible before i commit too much time to a certain design.

That's a pretty wide variety of tasks and each single one can be time consuming on its own. For your camera modifications they are all located in a drop down menu in the Creation Kit as for locking on and animation modifications those are really complicated and tricky i played around with only one creatures animation files for days before I finally had to just admit defeat and give up. All the other stuff sounds relatively possible The best place to start would probably be the Creation Kit Tutorials and search for each individual task there using the search bar:

https://www.creationkit.com/index.php?title=Category:Tutorials

or the NEXUS Tutorials:

http://wiki.tesnexus.com/index.php/Category:Tutorials

You are basically building a completely new game so just go with Unreal Engine 4 or Unity instead of trying to crowbar this into a game not built for it.