Nexerelin doesn't use the .faction tariff values; maybe I ought to make it do so.
In Nexerelin/exerelin_config.json there's a baseTariff variable and a freeMarketTariffMult (for markets with the Free Port condition). There's no way to set tariffs for a specific faction unfortunately.
Thank you very much for the immediate response Histidine. I first looked at exerelin_config.json which led me to google this thread after inserting public static boolean followersTariff = 0f
into Followers faction. As you said, neither subtype attempt has been carried on into the game. I'll play around with the code some more today and see if I can't figure out java.