Thanks for your tips. In fact the problem was in other part of the mod. I've successfully changed some aspects of this questions, and perhaps you find this information useful:

- I've changed thrace from greek to eastern culture only in descr_sm_factions with only some minor changes in export_buildings. It was very easy because the eastern factions and thrace shared exactly the same buildings.

- One of the factions in the mod was masking the seleucids, but I wanted this faction to be under the senate.
Using
superfaction romans_senate
on seleucid hasn't any effect.
Keeping the superfaction and changing the culture of seleucid from greek to roman again has no effect.
If seleucid faction is substituted by romans_scipii (lots of changes in descr_model_battle, descr_model_strat, export_descr_buildings, export_descr_units, descr_names, descr_character, descr_banners, descr_sm_factions, descr_strat, descr_win_conditions...) then the senate acts as it should.

- The campaign doesn't accept an "external" faction as culture tag in descr_regions or as faction_creator of settlements in descr_strat. I had CTD when clicking on a rebel settlement because the creator and culture was seleucid, that it is not in campaign any more, although it is defined in descr_sm_factions.

- The senate offers as a reward to the masked scipii a unit of triarii, in spite of the fact that triarii is a unit not assigned to scipii in export_descr_units. I expected a CTD when the mission was successful, but the triarii (with card of peasant, of course) was added to the scipii capital.
Thus I tried to get a CTD fighting a battle with that unit, but surprisingly it was possible to fight the battle, and the unit had the texture assigned to julii.

This is another proof of the hard-coding of some roman units that I described in other thread. https://forums.totalwar.org/vb/showt...91#post1065791

In this regard, could anybody give me a full list of units offered by the senate as reward for successful missions?
Does anybody know if it is possible to change those units?