Gta sa gangs function similar but not entirely the same as cartels, i would love to see the option of making factories to produce guns for like 300 pp and 100 manpower, i would say its reasonably low as well as not unreasonably high for it to be at this price, also you could make ways to travel to other places of the map.
One of the first things of course you should do is add all the gangs in(including those outside of los santos mentioned on the wiki). After that you could add other locations controlled by stuff like police, mafias and other small insignificant locations like drug buisnesses and other areas of the map which serve no other purpose than to make it possible to actually move from city to city.
OTHER CHANGES THAT WOULD HELP:
Township being able to engulf any of the insignificant locations around the map as well as being able to take out drug buisnesses running across the state.
The national guard being able to take over townships and other insignificant locations across the map without war.
Gangs being able to take control of the drug buisnesses running across the state.
Small drug buisnesses being able to run eachother out of buisness.
Ocean docks having 1 factory.
CHANGES THAT WITHOUT A DOUBT YOU SHOULD DO:
Focus trees for each gang and town, different generic focus trees across the other insignificant locations across the map( ex: buisnesses having the same tree as eachother but also a different one from the other parts of the map)
Each gang having a different focus tree from eachother.

Btw none of these changes are genuine improvements that everyone wants, they are just improvements i see making sense in this mod, hope you implement at least one of these changes tho...