I would just like to preface this with that most players aren't AIDS when it comes to exploiting the group system. However, there are some people who play mainly Kavala Rats who frequently exploit this system.
My idea is simple, implement exactly how Olympus does groups and gang initiation. Taken directly from the Olympus website, "gang members need to actually have gang tags in their name for them to be engaged, and, if you choose to wear gang tags, they MUST be displayed at the front of your name."
I think this goes without saying that this would make initiation in crowded places like Kavala much more manageable.