For Factions, I believe there should be a whole new Solar System for it. One basic Idle planet where Factions can meet up and be in peace. Then of course, each Faction's very own planet. Where they hideout, protect, and plan their attack against other Factions. It would act like Basing in a whole new way, which would allow rewards other than items and gear as well. Each individual planet could also inhabit their own type of minion that would fight for them to keep away other factions.
Faction Ideas:
Faction 1; Fire
Description; There's always an evil lurking, the devil of the Factions. They are the most feared Faction out of them all. They sustain a powerful anarchy and lash out at their enemies with all they've got. Their gear is untouchable by others due to a strange fire-like aura that cloaks around them. Beware of the Fire Faction, they will kill without remorse.
Faction 2; Earth
Description; The Earth Faction are more past times. They like to keep things simple and original. Some say they are part of Skyworld and with that comes perks. They are able to become one with the ground they stand on are excellent trackers. Beware of the Earth Faction, they can blend it with their surroundings and stealthily attack their enemies.
Faction 3; Water
Description; The Water Faction are said to be able to swim deep within the ocean. Since their planet is almost entirely water, this is a superb advantage. It is even said that their sky sharks kill their prey with one vicious bite. Beware of the Water Faction; their weapons aquatically advanced!
I would go on, but I'm assuming you got the idea. This is just a basic idea I had in mind, and the Factions would definitely be futuristic based rather than elements.