The sky dimension's original design (closely or differing with structures like we have with the End City rather than just like I've come across with mods no structures or dungeons spawning in them) being possible besides just The End. Unique mobs maybe instead of sky zombies/winged mobs, maybe one new ore/decorative block or weapon like we have with the trident. Too many possibilities but what to put together. I think an Aether is good but I'm thinking about something not too close to the mod like the Gravitite ore, it's dungeons/bosses/mobs and tool/armour sets which are great but to make it feel like a Vanilla update that suits compared to what they may do like they did with Drowned and Husk or the End City's good use of the Elytra but the enchanted weapons to me isn't that appealing really.
The Meaning of Life, the Universe, and Everything.
I concur with this idea too. More exploration and gives the ability to gather different crafting materials for future craftable items. Also makes sense to have a type of Heaven when there is already a type of Hell