Disclaimer:
Personally, I do not agree with the concept of sub-trees itself. However, based on the current existing mechanisms, I will discuss the ‘validity’ of certain nations joining the Korean TT. Please note that this is an examination of logical validity, not a claim that ‘it should happen’ or ‘it will happen.’ Also, I have excluded nations that already exist in the game as main trees or sub-trees.
Since you have already explained the Philippines, I do not need to mention it again.
As for Poland, I think being a sub-tree would be a waste of its potential. It would be better for Poland to form a Eastern Europe/Visegrad+/West Slavic TT together with the Czech Republic, Slovakia, and Ukraine (excluding donated equipment). In fact, I was a supporter of a V4 tree even before Hungary became a sub-tree of Italy.
In the case of Türkiye, given not only the relatively recent K9, K2, and KT-1 but also the long-standing technical and military cooperation, it wouldn’t be strange. However, I believe it is not impossible for Türkiye to have a standalone tree.
Vietnam has complex characteristics, having traditional ties with North Korea while recently engaging in arms deals with South Korea. For Southeast Asian nations that find it difficult to choose between China and Japan, the Korean TT could be an option.
Iran has ties to both North and South Korea (during the Iran-Iraq War, North Korea supported Iran, while South Korea did not explicitly side with either but sold weapons to both Iran and Iraq.), with relations with North Korea being particularly prominent. I likely don’t need to elaborate on the technical links between modern North Korea and Iran (MBT/AFVs, submarines, missiles, nuclear weapons, etc.). Furthermore, since Iran is not ‘Arab,’ it does not hinder the potential for a future Arab (League of Arab States) TT, unlike the Syria/Egypt/etc.
The UAE has very deep political and military ties with South Korea; there is even a domestic issue in SK regarding a secret alliance treaty that includes automatic intervention. (The detailed context involves sensitive political matters, so it is inappropriate to discuss here.) Even aside from this, SK and the UAE share deep relations not only economically but also militarily, technically, and diplomatically. ROK Army troops are stationed in the UAE for ‘military cooperation purposes,’ and SK’s ADD (Agency for Defense Development) has opened a regional office in Abu Dhabi. It is highly unusual for a military weapons research institute, a key national facility, to establish a branch overseas.
