First, and most importantly, I'm assuming that it's an "all or none" sort of thing when you decide to retrain an archetype. But, the way it is written, it doesn't specifically say that AND it also doesn't specify what is my primary questions here:
:: If a character has Archetype A, can he retrain out of an ability he doesn't want and keep the rest?
:: If he can, could he then retrain into an ability from another archetype that fits that same slot?
:: If both of those are viable, as an example, could a Phalanx Soldier Fighter retrain out of "Stand Firm" (L2 Ability Swap) and then retrain into "Pole Fighting" (L2 Ability Swap from Polearm Fighter)?
I'm sure you can see where I'm going with this. Again, I'm really just looking for clarification if anyone has seen anything official/semi-official regarding retraining (I looked and couldn't find anything) or in general what you as a GM would allow.
Edit: I just re-read this section in Ult. Campaign and my assumption seems correct, I missed a sentence when I first was reading this, so I guess my questions above are more of a "would you allow" than "is it RAI" - obviously as written it's intended to be all or not.