I know it takes more than just a config parameter but a rework of the simulation routine for missiles.
Probably not related to default ArmA 3 weapons but a really nice to have addition for Mod/Addonmakers: include terrain following simulation for guided missiles (AGM-84 as example) so missile will follow a contour flight path. Probably configside needs 2 params: enable/disable terrain following and average height above ground to maintain.
terrainFollowing = 1; bool to enable/disable the feature
avgTFheight = 25; height in meters above ground