Check this out.
https://forums.totalwar.org/vb/showthread.php?t=94653
I made an edit to the files that enable the Augustan/Imperial Reforms it after the first year.
However, you can change it to much later if you wish. Also, if you look in the modification sub forum, there are other as well, and different way to explain how to do it incase mine are a bit too complicated.
Good luck!
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