What's funny is I think these characters could have been done well enough, if they had any sort of setup whatsoever. Instead of making them all friends in the begining, they could have made it a real come up story.
Maybe the Boss is part of Marshall who you fight the gangs in Santo Ileso in several missions that both serve to set up Marshall, the boss, AND the rival gangs. In these missions you get glimpses of the people who will become your friends later, for example you see Neenah driving for Los Panteros. Kevin holding parties. Eli doing...i dunno something.
Point is, one of the missions with Marshall goes sideways, and the boss learns that Marshall is only purging the gangs in order to push a new drug onto the street. The boss gets fired and forced out leaving them alone and broke. Here is where you as the player have to do some side hussles to build some rep and some cash. During these hussles you get in with some side people that start to respect you and want your help in running "business" thus you start to build a little crew. The main casts each gets betrayed in some fashion by their gang and end up falling in line with you which spurns you guys to make the saints and really push to start taking over the town beating Marshell to the punch in stomping the other gangs out until finally dealing with them.
The overall plot idea is sooooo FUCKING EASY it pains me that these dumb fuck writers can't pull a decent idea out of their ass while getting PAID for it.