I posted in the chat suggestion however this is slightly differnt so thought I could try starting a post seeing what people think and making changes to it.
Club House Could make them like much smaller factions that dont war. Upkeep along with a cash cost to hit max members. Crime exp gained while in club will increase its rank. You lose 1% a day so must stay active to increase rank. The potential to have group crimes linked to this is there. A group banking like faction that gets 10% of the take on all crimes done by group members as membership fee. Perhaps other upgrades like a private poker table. Limit to owning a group and being into say up to 3 in total. If you dont want one you can join 3 or have 1 and join 2.