No one official. This is my interpretation of the rules
as written.
I think your players build, ss'ressen who wants to be a sage/artificer/intellectual is fine (choices have consequences, and they are fine with the RP disadvantages) except in 1 aspect, the flintlock. Expatriate is not an issue, the build falls apart with the rules for flintlocks. Unless I read your notes wrong and really your player wants a ss'ressen rifleman. If that is the case then what you have described it not legal. Side note this entire conversation would apply to kio swords, and being an expatriate in the League of Princes.
Expatriate does not make you a citizen it makes you a resident. Resident of Altheria does not equal citizen of Altheria. Just like in the real world being a resident of a country does not make you a citizen of that country. In the 3.5 campaign there were 2 certs released that granted citizenship and force you to forfeit your prior citizenship, the Laurels of Vigilance, and the White Sash of Purity. When the Laurels of Vigilance were released again in ARPG and 5E it did not grant citizenship.
How many modules have you seen where outsiders to a community are not welcome, I have yet to see a dwarven merchant who has been fully embraced by the NPC of the non-dwarven community they live in, regardless of how many years they live there. (The Horror Within, Unabated and Envenomed) And dwarves don't have the hatred that ss'ressen in Altheria have to deal with.
ACS pg 359 wrote:
However ss'ressen are typically viewed with suspicion, due to the Republic's long history and near-constant state of war with the Ssethregoran Empire.
As far as I recall only 2 groups of people are allowed to legally carry and purchase blast powder from the a Temple of Althares Vals (high ranking) and citizens of Altheria.
ACS pg 215 wrote:
Altherians, as well as clerics and holy champions of Althares, may purchase flintlocks at the listed price and may carry them regardless of rank.
There are no blast powder merchants. It is sold by clerics inside the Temple of Althares. They make the powder, and they sell the powder. Everyone else must keep a flintlock hidden or it will be confiscated by Altharians as it is considered stolen items. This ruling does not change from nation to nation, because the Clerics of Althares are the ones who enforce it. It seems like they are a tight knit bunch like when they lied about Althares revoking the ability to make blast powder to lower the amount being sold to the other countries. (ACS pg 216) Note to toodeeps's comment Brood of Ven are NOT Vals. (5E Ssethregoran book pg 245) They cannot purchase flintlocks or blast powder either.
Flintlock does not equal intellectual. While flintlocks are interwoven into Altherian culture, the flintlock is not the divine weapon of Althares. So if they want to play a Tinkerer, knowledge loving, ss'ressen in Man's World who is not held back by the Matriarchs go for it. Change the weapon. There isn't a flintlocksmith in Altheria that would sell an above board flintlock to a ss'ressen.
Ss'ressen walking into a flintlock store in New Althre
I'd like to buy a flintlock.
No.
But I'm Altherian.
No you're not.
I've lived here in exile for 5 years.
So sad, still not Altherian.
This is outrageous I'm an Altherian.
Prove it.
I was in the Shining Patrol, here is my Pin of Service. I killed 50 ssethrics with my marksmanship.
Go to them to get one requisitioned.
I'm not serving now, I left service to adventure.
You're not an Altherian, you're not a Val, you're not an active member of Shining Patrol. You maybe the best shot north of the marsh but you can't buy or carry a flintlock. Thank you for your service at the marsh, please leave my shop.
Could a ss'ressen purchase a flintlock and blast powder from a black market? Absolutely! But that doesn't match what you have said about the character's personality. It seems they want to be above board on all this. Also I believe with the changes you'd have to make means you can't start with a flintlock, the player will need to find a certed one. Still every honourable Altherian, and Cleric/Holy Champion of Althares would see it as their duty to confiscate the stolen goods, and report the character as a person of suspicion, as a GM I would warn anyone illegally carrying flintlocks of gaining infamy if caught by Altherians. The rules say enslavement, maiming or death are typical forms of punishment. (ACS pg 361) In the 3.5 campaign there was a series of modules in Old Coryan that lead to an Altherian monk who was fleeing Altherian with a huge shipment of blast powder, he was getting paid enough to start a life very far away from Altheria. The information provided about how strict the Church of Althares is about their blast powder was very helpful.
That character is not legally able to purchase flintlocks or blast powder. The player has many choices on how to fix that depending what they want.
If they want to be intellectual loving ssethric, just change the weapon.
If they want to shoot guns (pew pew) change to an Altherian born Dark-kin (very rare occurrence to have Dark-kin born in Altheria for some mysterious reason. Legacy of Damnation pg 18)
Or if they must be ss'ressen and have a flintlock change the personally become a lowly dishonourable ss'ressen that would deal with black markers, and has no qualms carrying illegal items with them.
I hope it helps.