For the technology group mapping, it look like the current system relies only on technological advancement of nations in CK2, and the Western technology group is assigned to most advanced nations from CK2 relatively to other nations (the absolute value of advancement does not matter) and the lower groups are assigned accordingly. For my conversion system worked fine when I converted game from end-game period (1453), my nations with Byzantium got Western tech group, while France that was fairly behind in technology got Eastern. But this system produces strange results if game is converted out of box from 769/867 bookmark, but for me it's fine, as it was designed to continue game from 1444. And I like the fact that the system rewards your investments into technology development, rather than being culture-based.
Its working as designed, and during the time of 769 and 867 it isn't far fetched to put the Indian's as the strongest technologically. That is how the history files for CK2 are scripted. How it is right now is that it calculated a median value of everyone in the world, those that hits over that mark with a good margin becomes western, if you are near the median then you are eastern and if you are way below then you get something much worse.
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