Planning to try my hand at modding this game so decided to try with a simple overrepresented type of mod - companion tweaks. After researching manuals and structures of a file I have a few questions

• No matter how small change to companion class and/or levelling plan is, only way to implement it is overwriting entire tree? So it is for example impossible to create small injection mod that would turn Sarafen from no subclass SC barbarian to SC fury shaper, it doesn't matter that is it essentially just addition of free skills - it require replacement of entire "Game.GameData.CharacterProgressionTableGameData, Assembly-CSharp" block related to his SC barbarian choice, right?
• UI restricts amount of class choices to 3 no matter how many progression tables you make. So for example it is impossible for Aloth to have choice between all available wizard subclasses - even if there will be table progressions for every version, only three could be shown during recruitment phase?

57 minutes ago, Desmodeus said:

Planning to try my hand at modding this game so decided to try with a simple overrepresented type of mod - companion tweaks. After researching manuals and structures of a file I have a few questions

• No matter how small change to companion class and/or levelling plan is, only way to implement it is overwriting entire tree? So it is for example impossible to create small injection mod that would turn Sarafen from no subclass SC barbarian to SC fury shaper, it doesn't matter that is it essentially just addition of free skills - it require replacement of entire "Game.GameData.CharacterProgressionTableGameData, Assembly-CSharp" block related to his SC barbarian choice, right?

This is my understanding but you can add an ability to an existing tree through a mod dedicated Gamadata item. But the whole existing tree would be affected, not just Serafen's. You can't add an individual ability to an individual character.

7 minutes ago, Elric Galad said:

This is my understanding but you can add an ability to an existing tree through a mod dedicated Gamadata item. But the whole existing tree would be affected, not just Serafen's. You can't add an individual ability to an individual character.

Well I am not exactly trying to switch abilities barbarian has access to, only change subclass npc is having or order of abilities he is getting on specific levelups. Pretty sure it shouldn't affect entire tree

the characters.gamedatabundle links to the PT_Serafen table 

4d20749f-17b8-4ddf-9517-e5396172c99a

But he has more tables in the progressiontables.gamedatabundle, so you'd have to see how each of these might interact.  Does all of his PT_Serafen abilities exist with other abilities if you choose a multiclass? I don't know.  Are his tables special or do they only have the same abilities as everyone else?  PT_Serafen certainly has different abilities but I'm not sure about the rest of them.  It looks like you'd just have to replace the 

PT_Serafen_Barbarian

table but that's from my cursory view.  It would be an easy copy+paste job, I think.  Usually all of the PT tables are independent of each other, so there is a new one for each variant.  Alternatively you could use the append method to add the subclass abilities to his tables but that would be more difficult because subclasses have different versions of abilities already on those tables.