First of all, I would like to write that it is fantastic that you are adding the Polish-Lithuanian Commonwealth faction. Unfortunately, Poles will not be able to play in their own language because the game does not even offer Polish subtitles. The basic version of the game released in 2005 even had Polish dubbing - prepared by CD PROJEKT with the participation of outstanding voice actors - unfortunately, I was probably too young to play strategy games then and now, after many years, I cannot have full experience, unlike many other players from Western Europe and the rest of the world.
Please reach an agreement with the creators of the Polish version and make them available as part of the definitive edition. Even though the CD PROJEKT department responsible for publishing games declared bankruptcy, obtaining the rights should not be a problem as other companies have managed to do so.
Unfortunately, this problem concerns a large number of games that are managed by the Polish branch of Xbox/Microsoft. I hope that the change in management and the huge number of potential players thanks to Xbox Game Pass will make it profitable to invest not only in subtitles but also dubbing for AA productions.