It would be cool if instead of every so many nights a Crimson Moon appears, if you could add a way to summon a Crimson Moon. Either via an item or ritual of some kind. This would be especially helpful for servers where players may not want to keep encountering Crimson Moons won't keep having them occur, but players who enjoy it, can start the event.

There's actually a "Scarlet Gem" item that can be right-clicked to summon a Crimson Moon. It doesn't have a recipe, but I figure modpacks can add their own if they want to enable it.