Need Changes
A big change made by this mod is a significant topology shift of the existing needs supply layout.
In the base game, a star design with Latium as the center is used because it is more streamlined and easier to balance. This allows the Celts and Roman-Celts to operate largely independently from each other while still both benefitting from importing and exporting goods to Latium.
This mod changes it to a more linear design where the Celts are largely independent, the Roman-Celts use some Celtic produced needs, and Latium uses several Roman-Celtic produced needs.

NOTE: Beer can now be made less efficiently by Roman-Celts from wheat. Celts can now also make wine less efficiently than Roman-Celts. The most efficient methods remain Celts making beer and Latium making wine.
Why Change it?
- It's different and interesting
- It allowed moving chariots to the Roman-Celts, adding some new needs, and removed importing soap and fine glassware from Latium
- I think it still makes decent sense since the Roman-Celts are now the cultural bridge between the fully Celtic population and the proper Latium Romans
The Downside
With the Roman-Celts now supplying all the Albion goods to Latium the balancing will probably favour more Roman-Celtic islands to supply enough goods. Some aspects of this will be alleviated a bit because there is now more population and belief buffs due to how the public buildings have been merged and the addition of bread/beer to the opposite type of population.
If anyone plays the mod long enough that this becomes a problem please feel free to give me feedback via comments on the mod.io page or opening an issue on github. Information on what is the bottleneck and any estimates you have for changing the need consumption rates or production times will be extremely helpful for making balancing changes.