With the current level of procedural generation and graphics technology, assuming fidelity equivalent with existing Odyssey assets, landable...
● Barren thick atmosphere storm worlds (Titan, Venus, LV-426): Very easy to do. Thick particle effect systems, atmospheric simulation force vectors and lightning flashes already exist in the game because of the thargoid maelstroms. All you need is additional procedural systems for creating the weather fronts. If the world is in a high population system and a candidate for terraforming, the surface would receive terraforming facilities, like the ones you see in the movie Aliens.
● Gas giant upper atmospheres: Easy. Procedural systems that can populate the skies with various weather fronts, storms and rains. Then you'd just have to figure out the lore of why CMDRs who eject somehow don't die.
● Thick atmosphere desert worlds (Tatooine, Arrakis, Hoth): Medium difficulty. Procedural systems to populate the skies with clouds that match the Stellar Forge planet texture from space, but with polar biome difference with potential snowfall, and changing polar regions based on seasons. If the conditions are right, commanders can remove their helmets on the surface. If it's cold or hot but not deadly, standard Odyssey environmental hazard mechanics apply.
● Water worlds: Hard. In addition to clouds and weatherfronts, you need procedurally populated glaciers that change based on seasonal drift of the winter region near poles. The calculation of where this region is is easy because it's just a matter of temperature and pressure but actually creating Earth-scale polar regions with thousands of square miles of desolate ice mazes is not a small task. Also, many water worlds have wildlife. Making a few animations of non-identifiable aquatic beings bumping the surface sometimes is not hard. Flying animals would also need to sometimes be in the skies. But you would not be allowed to dive underwater because generating those biospheres with enough complexity and variety across worlds is not feasible.
● Ammonia worlds and Earth like worlds: Impossible. To populate tens of millions of 1:1 scale Earth like worlds or Ammonia-based biology worlds with their separately evolved unique biospheres with dozens of different biomes seamlessly meshing with each other, with realistic erosion signatures and water and weather systems, hundreds of millions of completely unique plants and animals, complete with strangeness brought on by tidally locked twilight worlds, high-gravity crusher worlds and neutron-orbiting gamma hell worlds, you would need technology that simply does not exist yet. The minimum level of detail is E: D Odyssey. A singular square inch is the smallest detail that needs to be perfect. Every square inch of tens of millions of those worlds has to look as high fidelity as every square inch of an Odyssey settlement or planetary rock texture. The Cobra Engine is not The Matrix.
● Human-populated desert, water, and Earth-like worlds: Beyond reasonable by any conceivable measure -impossible. Combine all that was listed previously, and add to that the procedural generation of 1:1 Earth scale 34th century total human sci-fi infrastructures supporting the lives and industries of billions of people per world. Thousands of nations. Hundreds of cultures. All influencing the cities, architectures, languages, fashion, music. Billions of kilometers of highways with thousands of brands and models of vehicles. Sea lanes with cargo ships, cruise liners and recreational boats going around. ...and even if it was possible, which it isn't, it would not be allowed, because human societies have children and sleep schedules, and in E: D you aren't allowed to shoot a child, a sleeping person, or any unarmed person, due to ESRB age ratings.
However...
● Water worlds and human-terraformed Earth like worlds, with shuttle rides from orbiting stations onto limited exploration human infrastructure on surfaces: Surprisingly easy. Just fake it until you make it. Some procedural tech to create a skybox around the place. The player can explore a section of a city or an outpost on foot without the ability to leave, and can see what's in the horizon outside the explorable area, whether it's wilderness with trees, countryside, cities in the distance or giant skyscrapers right there around you, with the current controlling faction's or power's banners flying. Plants imported from Earth use common models. Birds in the sky are just birds from Earth.
galaxy having one variant of star and one type of planet.
= 560 upvotes and 161 comments. It's still a popular request on the ED subreddit.
