Even if the 'gangs' are your main focus now. You should be fair to everyone that only want to play as an individual and give alternatives to defend themselves against gangs that love to attack them instead of hitting adversary gangs.
Provide a shield or a specific facility to be purchased by individual players in order to buy some time to collect the resources needed for an update and a saved point for units if they get attacks from gang members.
This is needed and is the number 1 reason why people will leave the game, and why many have already left.
The game rewards high level players for farming low level players. The game offers no mechanic for new players other than rebuild completely every time someone stronger destroys 100% of your units with less than 1% of their income.
The natural result is far fewer players staying until you have nothing but a small number of higher level people playing a dead game.