The number one thing I consider is that the inevitable End update should be very different to the Nether Update. Many datapack/mods I see for the End often mimic what was done for the Nether. I sought to make additions that added to the End's visuals while maintaining similar infrastructure of buildings and emptiness of the void.

Progression should be different from the Overworld and Nether as well. The End and its inhabitants express a strength in its magical essence. So, progression should mimic that. Using Amethyst, players are to "transmute" items into different forms to gain their functionality. The base example is that those living in the End don't need to smelt chorus plants into popped chorus, when instead they can transform it with the magic of amethyst.

Every update to the game should integrate with previous items, giving them new functions. I've used this idea to give more use to various items and blocks. Of course, the biggest is Amethyst. It is the foundation for harnessing the new powers of the End. Other items include sponges, froglights, copper, phantom membranes, and pitcher plants, to name a few.

I believe End Armor should not be an upgrade to Netherite, but instead be an alternative upgrade path. This armor is similar in stats and uses diamonds as a base, but has different functionality to better match the End.

Many concepts were based around the End additions found in Minecraft Dungeons. Some structures are designed closely after parts of that world. The fauna of the End Wilds is mimicked by the plants in the End Midlands biome (we have so little yellow plants currently lol). This concept also includes two variants of endermen found in the outer islands: Watchlings and Snarelings.

For those who have achieved Overworld-End teleportation, note that the teleportation occurs at EXACT coordinates. Be mindful/prepared for natural generation.