playing as the romani, I changed the script to have the marian reform happen earlier, because... it's too long to wait with a slow laptop and hard refraining myself to win the game before it. It is surely not historical, but past 200bc there is not much left of historical evolution.
So I wanted them to happen in 192bc, just to enjoy the use of these cohors reformata. I did only change the numbers of turn in the ebbs_script (Rome - Total War\EB\Data\scripts\show_me\ebbs_script), as follow :

under "Marian trigger", "conditional reform" :

;Conditional Reforms
monitor_event FactionTurnEnd FactionType seleucid
and I_CompareCounter Romanii_Reform = 1
and I_CompareCounter Latifundia > 6
and I_TurnNumber > 319
and I_NumberOfSettlements seleucid > 44
;and BattlesFought > 249
and I_CompareCounter ReformatorCounter = 1

I changed the turn number from 399 to 319, making it 20 years earlier (80 turns), from 172bc to 192bc -correct me if I'm wrong.

Before that I tried, with a game saved in 178bc and all requirements needed, to make it happen in 177bc, and it worked (changed turn 379), I got the reform, the barracks, and could recruit marian cohorts. So it seems to be save-game compatible too.

The only questions here are... did I forgot something? Is this reliable to play? Will it affects the Augustian reforms?

I'm starting a whole new campaign on huge size to see if it's ok... but maybe you could prevent me from losing time!

Thanks!

Ah and by the way, does anyone has successfuly modded the game to give polybians principes lorica segmentata?
Ouch! Argh! Stop throwing pila, just kidding!