In the days of Arma 2 and Operation Arrowhead, terrains had the ability to utilize the horizont object to create mountain ranges or other skybox objects that would help to further immerse the player in the environment. Unfortunately, in the move to Arma 3, it seemed that that ability disappeared when the same horizont objects were tailored to function as a blend between the ocean and the sky for island maps. This tailoring, from what I've been able to gather, is primarily an added influence from skyColor and fogColor over the horizont object. Some maps have managed to work around this by endlessly tweaking fogColor and skyColor, but to be able to change how much influence those two factors have over it would reduce the workload significantly.
As CfgWorlds classes exist, they have a parameter named skyColorInfluencesFogColor by which old lighting configs made before the Arma 3 Visual Upgrade work. My suggestion would be to follow up with new skyColorInfluencesHorizonColor and fogColorInfluencesHorizonColor float or bool parameters to adjust either how much influence is had over the horizont object or whether it is influenced at all.
