The Soul Cairn is a very interesting place, but apart from the three/four vanilla quests that it offers, there was no real reason to come back to it later in a playthrough.
With three quests, including references from The Elder Scrolls: Battlespire, here comes More to do in the Soul Cairn, some fish with Soul Cairn Fishery and a house with Soul Cairn Shack!
The free Creation Club Fishing creation introduces new fish in Skyrim, with the possibility to put them on plaques or in aquariums. Being a huge fan of The Legacy of the Dragonborn, I thought that I could create a mod where it is possible to collect all those fish, have them living freely in an establishment, with a curator and visitors.