There was another problem with Rome 2 though. CA developers were very lazy with those standard bearers and didn't create animations for them. The standards were held in right hand alongside shields, and weren't even considered standards by the game, so the game determined them to be
spears.
The result was that standard bearers
used their standards to fight. And they incorrectly held it like spears even when not fighting, so they pointed them towards the enemy like common spears or pikes when they brace.
Where in the world do you ever see a man in the Roman First Cohort using his golden eagle like a useless spear, banging it against shields? Or a Persian ring standard being used as a weapon? The standard bearers would've been flogged and executed if they disrespected the standards in this fashion in reality!
As little I as I have played Attila, I am not sure if this was ever fixed. So even if you can mod in the awesome RTW style banners somehow, the soldiers holding them will use them to fight and kill enemies instead of using swords.
That would look very awkward - killing men with a piece of cloth or a pretty statue on a stick.