i think adding optional side content that you can only find by exploring by yourself will be a big improvement. instead of it being a marked location you will have to explore the map to find it yourself, kind of like the meteor from the first game or the mercury 2 logs from below zero.
i guess the degasi crew from the base game would be a good example too

i was hoping we could have science side-quests to study the local flora and fauna to discover and teach the player about creature behavior and learning to harness it: https://subnautica2.nolt.io/8257
the big clam would be a perfet example for it - you would have to find it all on your own. currently scanning it gives us a database entry and nothing else. but with that starting a quests exploring more of it unique mechanics with some NoA lines and expanding on with more gameplay would be very interesting. on the other hand it wold remain entierly optional.