Help with faction's culture shift

[Callicles]

True. I meant more broadly the culture shift. Would changing a faction's culture affect things other than just aesthetics. For example, if as Pontos I conquered a settlement held by the Seleukids, would there no longer be a culture penalty? I assume so.

[Senshi]

If you change the culture as coded for the faction in the descr_sm_faction there might be a gameplay impact, I think. Some of the "special buildings/wonders" give boni only to certain cultures (e.g. Foreign Sea Trading Posts in Iberia giving boni only to Barbarians) etc., also the penalties when conquering a different culture's town might be lost.
This is only my assumption based on my poor knowledge of the game mechanics, perhaps the modding professionals here can give you a more fact-based answer ;)