4 turns per year ? you can build an empire with in , let say 20 to 30 years ! so , Rome + 50 it's ok , but the time frame should be much shorter to make it harder . in vanilla you have only 568 turns , and now ? 1,136 !!!
272 bce to 90 bce = 728 turns , to much !
Let us follow the Romans , they build their empire from 275 bce to 43 ce , but , and this is a big but , from 146 bce they were the only empire in the western world with no true rivals but groups of "Barbaric" tribes .
272 to 146 = 504 turns . the bug is the Marian reforms...that started in 107-106 bce...