Crazy, that sounds crazy, writing command in faction terminal, if i dont want to "raise influence" in cities. Practical problems: one member wants to influence, one not (wants to roleplay). Or even you can set it individualy, you will have to come back to base to turn off this option every time, you want to visit friends in city for small ingame chat? Well, that is very "populating city" idea.
Basic players or gangs (= players and gangs that dont want to raise influence in city) should not do anything. In comparsion with real life, they only visited city, nothing more. They dont "scare locals" for some black money, or ciggarets gifts. Also practical reasons.. after wipe, there will be much more players playing (i hope). So you will need to talk to every player who does not know about influencing and you will have to force them to "turn off" their influence. So basicly, you will kill them. (Imagine situation where you have incomming one new player per minute in city (because of basic set of quests) and you need "explain" everyone to get back on base and turn off influence...).
So my idea: Influence will raise only if you have special item (dog tag,...) in your inventory = 1/0 condition.
Or different idea, something related to playability, .. influence will raise only if you will have radio with local (city) radiochannel tuned in your inventory. There should also exist some mechanism to detect if you have radio tuned, maybe that basic message sended via that radio channel will always show up on over the player.
Or invent something different, but players who wants to visit city without hostility to current city influence owners should not do anything to prevent eliminating former gang raising their influence.