Advanced Planetary Features

When it comes time to populate the system with lots of planets and moons, I think a few features will come in handy:

• Ellipsoidal Shape: Rapidly spinning planets like the fictional Mesklin and the real world Haumea can be spun up to be oblate spheroids or triaxial ellipsoids. Even the gas giant planets are noticeably oblate. Also supports nonspherical atmospheres to match. Also useful for minor bodies. May require functional nonspherical gravity to get correct, but not necessary for the basic implementation.
• Axial Tilt: Tilting the axis of rotation by setting a specific Pole Right Ascension and Pole Declination. (Or Obliquity and Equatorial Ascending Node) This is vital for if people start making realism-oriented mods like a Real Solar System, or even if people want to do fun things like giving Urados and its future satellites a Uranian tilt.
• Texture-based Height and Color maps. Due to the cost of storing textures on a server, this feature may remove the ability for a planet pack to be shared with the built-in planet sharing tools, instead requiring that the planet modder host the planet pack on their own--but I'm sure that won't be a problem, given that websites such as Spacedock.info exist to host space-game mods. However, it is a vital feature for a Real Solar System mod, or mods which replicate existing known solar systems, or for adding large-scale detail that can not be done with procedural generation, like eyeball earths and water-tongue-world-types for tidally locked bodies, or other specific-shaped features.
• Multi-body gravity for binaries. While we should keep the simple patched conics for most of the system, in a binary planetary system it is necessary to have the spacecraft affected by both objects in the binary, as it's very difficult to imagine a patched conics approximation that can correctly handle trajectories for binaries, at the VERY LEAST requiring a manual override for sphere of influence, as the default calculation for binaries (that is, just a planet with a very large moon, no barycenter) will result in SOIs larger than their semi-major-axis. Things may get confusing when we try to mix one-body gravity with two-body gravity, so it may be simpler to simulate three-body gravity for spacecrafts everywhere, enough to simulate the effects of the Sun and two binary bodies if you're at the edge of what would be the binary's SOI.