Can't really see the gang getting to much hate from other crime orginizations.
Maybe each protag will also have a separate antag to their own story line.
Franklin = Gang Related, Maybe Lamar (is that is bros name, gta seems filled with traitors). Michael = guy banging his wife, also a snitch. Trevor = This is a hard one to make up, hmmmmm. Maybe another cop.
I'm probably the least f***ed in the head person in the world. I swear to god m8 everyones f***ed in the head.