Frankly, the Ferrus Darksun skin is so insulting they should just replace it and say the first one was a bug, that someone accidentally disabled half the layers or something. Give everyone who was foolish enough to buy it (me) the new version for free. Let the old one fade into obscurity as a niche oddity and mark of fiscal irresponsibility.
I also think they should make any reskins that use the stock models and just change the camo pattern something reserved for the docket shop. That level of effort isn’t worth the aquillas.
So taking in Archetype and not simply increasing the branches:
They could be as different from Ogryn is to Veteran, being gated to their own weapon pool (For example Admech being able to introduce mechanical weapons, like Mechadendrites; as well as many Admech only weapons, like Arc, Phosphor…).
The game impact would most likely be upon the narrative, where they would either have to find a candidate that can be considered as a ‘reject’ or a way to make a non-reject work in the player pool, as well as upon the balance, which would have to be ‘fixed’ after.
So an Archetype would have a quite steep cost, 3 or 6 VA (3.900+ voice lines for each), new models (Both character and weapon), new gameplay…
But it might be that offering it for free might be the best way to do it, and sell cosmetics (Krieg, Tallarn, Elysian, Vostroyan… Enginseer, Rogue Trader’s Tech Priest, various Skitarii…) instead.
Touch unobtainable chunk of lore to be used to fuel gameplay.
This mean that archetype are pretty limited to things that can sell part of the lore that the Veteran/Zealot/Ogryn/Psyker can’t.
Admech; Xenos (Though problem of being in the Reject/Penal system); (Ex-)Sisters; Squats (PoV issue)…
Those have enough depth to be able to survive and thrive alongside the current cast.
Reusing assets would most likely be to be avoided, to sell more cosmetics.
You could grow the tree sideway, increasing the total number of branches from 3 to 4 or 5 per tree (Prefer 5 due to keeping symmetry)
People will be angry at the point cost that would come from crossing from one side to the other, but honestly nothing force them to do so anyway.
I mean, they have, like many people want Servitor and Servo Skulls on the Tech Adept.