I think these are some important things Universe Sandbox needs now:
Save stars and planets as they are - When some planets and stars are saved now, planets sometimes change texture, and stars saved with "Realistic" off change properties.
Hills sphere - Just like in the old.
Background - I would be nice one could use what ever picture they like, as the background.
Axis value - Just like in the old one, that would make it much easier to adjust planets and stars axis, and also transfer stars systems from the old too the new simulator.
Inclination - It would be nice to have a funktion to make all inclinations 0.
Roche limit - Would be nice.
Trails - Custom trail colors
Atmosphere color- Custom atmosphere colors
Atmosphere properties - All atmosphere now spawn to look exactly the same, just different colors.
Craters - Maybe add a funktion to make craters disappear with time, with a value determining how fast.
Surface view - Dense atmospheres like Venus¨s should be dense enough, so that only the Suns light would be able to penetrate. Now, the background-image can easily be viewed through the center of the sky.
Impacts - If large enough, they should be able to make the planets deformed.
Lense flare - A funktion to make stars shine into the "camera", would make it much more alive.
Comets - Their gasses should blow directely away from the stars, but dust and ice should bent.
Clouds - Maybe a bit too much, but changing cloud coverage would be nice.
Textures - Texture editors, or the ability to "random" a planets texture to find the one you like, and custom textures and bumpmaps.
Objects - Like we have a teapot, pool-ball, and a bowling ball, i think we need a sattelite model and a space shuttle/craft model.
Planetary comets - Terrestial and gasplanets close enough to their host stars to become "comets", should loose mass with time.
Magnetosphere - A very simple magnetosphere would be a very nice feature.
+ AuroraPlanet brightness - I have noticed that Jupiter, Saturn and even mars and Venus are barely visible from the surface of the Earth - in the simulator. That should be fixed, also for other systems.
Create planet/star - When i create a planet or star, the properties often change back to the numbers it where before. If i change mass on a planet to 0,24 Earth, and then change the radius to from 6000 to 5000 km, it will change back to 6000. This can happen with densities and mass too. Very annoying.
Hope it wasnt too much.