I agree with you mostly.
Your first point about splitting gangs however, although I agree with it is a lot harder to do as people will often quit the server and cry that the admins are nazi's if they are being told they cannot play with friends. Imagine your in a gang with your friends and your one of the 6 in your gang told you can no longer play with friends.
I do believe that an 'unbanathon' would be beneficial and frankly, based on the facts ( GTA mass unban helped revive the server, Asylum mass unban revived the server ) it works very well when servers become dead. Especially because ARMAs no longer popular and there aren't many new players replenishing the player base o servers. Therefore servers rely on old players to return.
Another thing is, if the bigger 'farming' gangs became more cartel active, i'm sure the server would seem a lot more alive. People may think I have a grudge against Tree but I believe strongly if gangs as big and as active as Tree came to caps more often the server would seem a lot more lively.
Finally, to finish off. This server is completely known for its cartels and there is no denying it, this is the reason the server did so well against servers like GTA and Reborn. I do not at all think that this is a bad thing and believe that Olympus should embrace it as much as possible, ARMA 3 is a combat oriented game and despite retarded mechanics has some pretty amazing mechanics as well. Helping the fighting aspect to be so much fun.
Feel free to quote me on anything, these are just my opinions.