I have finished the first round of summarising balances and changes for existing civilisations. I will use this post as a reference to explain some of the logic.
I tried not to revolutionise the civilisations too much and keep some of the original design and yet trying to use as many good ideas as I have read around. The most radical case is the Armenians moving from ‘Infantry and Ships’ to ‘Cavalry and Ships’, but they are the most problematic. Moreover, a few holes in the technolgy tree are also maintained and certainly some things can still be improved.
Also for context, my elo is in the 1800-1900 range, and as much as I follow the competitive scene maybe there will be some balancing that will create unintended consequences. Bottom line, I have yet to point out any threads for rebalancing some units, such as Samurai. And there are also other civilisations that would need more changes, but that will be for a second round, by the time I finish pinning all the new civilisations suggestions that you have posted in the thread.