You know what I don't expect in an Arma campaign? Operation Trebuchet, Mass Effect Opposition, and ships from Blue Planet.
Nirvana is a custom campaign driven by passion, out of love for Mass Effect, the Expanse and especially
Blue Planet. There's neat stuff like a custom HUD that makes the shooting simpler to deal with because it can detect enemies through walls, simple mission design that takes a more action approach of ArmA's mechanics, lore and story that, while are definitely inspired, still manages to hold onto player's interests, and its own version of a Universal Truth.
How the hell do you manage to do a UT in ArmA, I dunno, but it was a very vivid experience.
If you have ArmA 3, I'd say it's worth a download with all the total conversion mods. It's more story driven than most custom campaigns, with cutscenes and use of custom animations in an attempt to immerse you into the story. I post screens of it occasionally on Discord, albeit on low graphics due to having a lowest end PC.
[Warning: Some of the weapons require DLC but the mod itself doesn't, notably Contact. Doesn't affect game experience but the modder didn't mention this at all.]