Hey, Safeman! I have a big recommendation for 1.3.6, or 1.4! I thought of a new event of some sort that has to do with meteorites...
What if there was a rare chance that when a meteor lands in your world after killing the golem or higher tier boss, you could find a rare otherworldly creature in the center that would trigger some kind of meteor shower once you kill it, and the meteors that fall have unique new ores and other things inside, as well as unique new enemies! This would actually be a better idea post moon lord, as it would add more elements to the game snd more things to do after moon lord. There could also be a unique boss in this event! Another importsnt thing to mention is that the special meteorites during the meteor shower event would not actually break any blocks so your world is safe. This sounds like a cool new event idea, just a reccomendation.