Yes, it's somewhat similar to what you have guessed.
For example, the Swadian Ranged tree is as below:
(Tier 1 - Peasant) (Tier 3 - Peasant) (Tier 6 - Veteran) (Tier 8 - Veteran)
Swadian Hunter --> Elite Swadian Hunter ---------------> Veteran Tilbaut Castle Archer --> Veteran Suno Master Archer
|
'---------------> Swadian Crossbowman --> Elite Swadian Crossbowman
(Tier 3 - Peasant) (Tier 5 - Veteran)
Now, if you buy the Swadian Crossbowman directly from the center, you can upgrade only
Regular --> Elite and not Regular --> Veteran --> Elite.
And, if you buy the Regular Tilbaut Castle Archer from Tilbaut Castle, you upgrade from
Regular TCA --> Veteran TCA --> Veteran Suno Master Archer, and it stops there.
This is because I have tried to provide reasonable upgrade paths while staying within the
framework of the Silverstag troop design, so some troop upgrades are missing in my trees.
I'm sure with more work and inputs from players regarding the balancing, it would become
possible to have better troop upgrade paths, but this is what I came up with. Also, the
upgrades from Regular --> Veteran --> Elite don't change the weapons and armor, and
paying high costs repeatedly for upgrading just the skills didn't seem to be worth it.
So, this is how it works across the board, with all the kingdom troops, except the Player-
made troops, because I don't know how to access that information yet.
Regarding direct purchases from the centers, the recruitment works just as it does in vanilla
Silverstag. You need Veteran recruits to buy higher tier troops. But, if you go the upgrade way
from peasant troops to higher level troops, the peasant troops automatically turn into veteran
troops, and if you dismiss those you get veteran troops in the center pool. All this is part of the
Silverstag gameplay design. I didn't do any work on it
So, in the above example, you could train your Swadian Hunters to Elite Crossbowmen, then
decide you don't want to stop there and want higher tier troops, so you dismiss the troops in
Tilbaut Castle (assuming you have the standings and affiliation) and get Veteran recruits in the
center, and then recruit Regular Tilbaut Castle Archers, and you can then upgrade Regular TCA
--> Veteran TCA --> Veteran Suno Master Archers, which is the top ranged tier for Swadia.
And this is doable across all the kingdom troops, with minor differences, except for a few
uniques which just did not fit anywhere in my troop tree branches. So those will be just like
vanilla Silverstag. You buy them from the center where they are available, and upgrade them
from Regular --> Elite, skipping Veteran. When you check the troop trees in Reference Material
--> View all Troops, you can see the upgrade paths, though the branches don't show because
Windyplains has taken the branching tree out of the presentation design.
As I understand the Silverstag design, the early game is meant to be played without too much
fighting except in tournaments, and doing quests for various NPCs to get standings and cash.
This cash should be invested in enterprises to generate your own income. This income helps
to recruit and maintain troops later on, since you now have high standings to access different
troops, and better reserves of cash, and continuous cash flow to buy and maintain them.
As I see it, the branching troop trees give the player the best of both types of gameplay, since
one can upgrade the already bought troops without too much grind, but with the costs being
close to buying troops directly, it doesn't give too much advantage over the AI.
Hope this explanation helps to understand the troop tree addition better. Cheers!