@GaeasSon
This is by far the most realistic implementation of the \"round worlds\", although it would require several steps of preparations and research. Current Star Sytem will have to be reworked. Instead of having 17x17 sectors of 2600m dimension, it would be required to have at least 5000m sectors in 9x9 matrix. That would be required to house bigger worlds with transition space and, in fact, will be more suitable to make more consistent sector features such as dense asteroid fields of certain type, more feasible for long-term mining, than it is now, or nebulaes, and also more convenient for large scale battles without dropping in-and-out between sectors.
Planets then can be made about to 3000m diameter, or 1500 radius. In this space the transition zone is placed looking like an athmospehere-shrouded terrain, just like we have it now, but as a sphere. When player goes trough the atmosphere, the transition is being run. Planet itself is completely flat 3000x1500 or something plane, that is basically Earth\'s flat map (google it), where North-South poles are stretched to form a rectangle. In order to accomodate the stretching, it would be reasonable to swap the positions of poles and equator in terms of terrain generation, so that stretched areas would stand for larger spaces, and give less space for generating poles.
To give you an image, that will generate a 3000x1500 map, in which each 1500x1500 square stands for North and South hemispheres, poles are taking circle in a middle of each of two, and equatorial area is generated all around these circles - in between them and on all map edges. For each angle of the planet the chunk is selected, so that when player enters the atmosphere, the engine will place his ship above the proper location, and when he takes off, it will move him in proper location near the planet.
Finally it will require a system that wraps the map around. When player reaches the edge of the world, that system loads the chunks from appropriate place and connect them to the visible world making a seamless connection. Right edge is continued by the left edge, and past top or bottom edges the player will see the same edge segment, but of another hemisphere turned 180. This will effectively make the world seamless and proper, just except that the only thing that stands in the way of ANY particular method of making seamless 3D world, if exactly, inability to wrap blocks to form seamless connections, is negated by ignoring the angular warping of the surface.
The substantial nature of the landscape remains the same - you have a flat world some blocks deep, theres an undestructible layer on botton, and gravity works straight down. It might be hrad to navigate those, but I guess a compass can be made that simply points toward North point, which is determined coordinate.