I really want to learn (or remove) a Caste talent

Caste talents are generally not something you can learn after character creation. OK, I understand the rule. But…

What if I play a Priest/Priestess archetype that’s not initially from the Priesthood caste? How can I “learn” the Priest talent, or will I never really be accepted among the priesthood?

What if I play a character that becomes a noble? Can I “learn” the Sheltered talent?

On the other hand, if I’m from the Priesthood caste, I keep the Priest talent even if I go against my upbringing and become a Mercenary. Why?

Characters with the Subject talent get “tax breaks” even when they are doing nothing for their lands (no longer herding or farming or whatever). When should they drop Subject? When is it possible to become the Subject of another land?

The caste Talents are supposed to reflect your child, teen or young adult life living and working as a member of that caste. Some Talents like “Sheltered” don’t make sense when you learn them later because they reflect basically years of networking and such. However, if you become a priest, the Priest Talent may make sense. And if you were a priest but are now a mercenary, you keep the Talent because you still have the connections to your former order.

As far as I understand it, caste Talents are intended to reflect the past of your character and not necessarily the present.

While there are no rules for this, the GM could allow characters to switch or buy new caste Talents if it makes sense.