NVG availability is set by the mission designer. the option is disabled by default. to enable it, open the mission in the mission editor, select an A-4E-C unit, then select the right-most option tab - this is a part of the same suite of tabs where you select the livery and loadout settings). There you can enable NVG equipment for the unit, and/or remove the ECM panel if you wish.
Note this same set of tabs also allows you to preset the radio frequencies used by the radio presets.
plusnine's post in Community A-4E-C v2.2 (October 2023) was marked as the answer