I am still wondering about giving the Getai stone walls. I mean sure, while the Dacian walls weren't neccessarily of the exaggerated size of the walls in R:TW, I still believe it would be a good addition considering
1) The Dacians did heavily fortify their cities/davas, with walls that were often 3m thick and over 10m tall, made of large stones. It's important to know that the Romans had such trouble with these fortresses that they were immediately dismantled after being conquered and the Dacian capital, Sarmisegetuza, was only taken by treatchery, which allowed the Romans to cut off the water supply to the city. While arguably, the Roman-Dacian wars take place a bit later than the game's time period, I would still suggest it because...
2) The Getai seem to have an obsession with turtling their one city and not moving, and perhaps stone walls will either make them more of a challenge for others to conquer or give them enough security to become more aggressive.

I just believe the Dacians are the most befitting of the Barbarians to get stone walls, given their historical ability to create fortresses which posed serious obstacles to the Roman conquests.

Well, these are my two cents anyway...