I`m not a modder, but I have some cool ideas for three characters mod. First, is it possibly to change skin of 2 unnecessary characters of the game to be same like CJ. Then it`s logically that you`ll be able to clothe clothes, to new 2 protagonists:
1. Because we want to fell ambient of GTA V in GTA SA it will be good if you can make other protagonists follow you, like homies of Grove Street.
2. When you play with one protagonists, others are just like peds, gang peds. They walking on the street and attacking Balls
3. When you have wanted level and you switch to another character you lose Wanted level
4.When you drive in car with one of theme, theys can take wheels and you just need to set point on map. Untile drive you can shot from the window in free style.
That is all. I hope somebady will know how to create mod like this one