An obvious fact is that, in the historical context of AOE3, Asians did not accept the diplomatic system invented by Europeans, and there were also no diplomatic titles like ambassador, minister, consul and so on.
On the other hand, from a game design perspective, having optional new Europeans and federal Americans for Asians should be considered.
One possible solution is add Advisor office instead of Consulate.
For example,
“Ever Victorious Army” (Chángshèngjūn) was a small imperial army that fought rebels in late-19th-century China. It was directed and trained by Europeans. The Ever Victorious Army fought for the Qing dynasty against the rebels of the Nian and Taiping Rebellions.
The foreign employees in Meiji Japan, known in Japanese as O-yatoi Gaikokujin (“hired foreigners”), were hired by the Japanese government and municipalities for their specialized knowledge and skill to assist in the modernization of the Meiji period. The term came from Yatoi (a person hired temporarily, a day laborer), was politely applied for hired foreigner as O-yatoi gaikokujin.
Foreign government advisors in Meiji Japan
It is difficult to find a historical context for adding Polish or Maltese diplomatic relations to consulate.
But it is much more reasonable to invite an engineering or military advisor from the same civs to the office.