I want to get into modding with the following goal:

I want to change many faction starting positions to make fewer, larger faction's. I would honestly prefer that there's only 1 Celt faction, 1 viking, and far fewer middle eastern client states for the sassanids.

Anyway does anyone know how to edit start positions?

Also i'd like to change the chances that the AI sacks or razes a settlement to be much less, making them actually occupy and expand sometimes.