Before some time there was the Imperial Crisis mod and now the Imperial Crisis II, a Russian-language mod developed by Asterion2005. As far as I have understood the mod is a patchwork of different mods, RS2, Fall of Rome, Invasio Barbarorum but also includes many Roman and Persian units that were apparently developed by the modder itself. The 3rd century Roman units along with the Persian are E-X-C-E-L-L-E-N-T and the overall work reminds almost a first class mod!
http://imtw.ru/topic/36497-%d1%81%d0...perial-crisis/