I think the true marvel of this game is if they can build simulation into the game play. If the missions are similar to other MMOs where one is railroaded into building X module Y times to accomplish the mission the game will be little different than any other MMO that requires you to grind.
But if they simulate the actual dangers and pressures of entering space the possibilities of this game truly excite me. For example if a player needs to build a space ship to travel from the moon to mars they have to take into account: solar wind, high speed particles and meteorites, deadly radiation, life support, power generation and many other variables. One may build a large enough functional life support system but it's size may be to grate to be protected by the radiation shielding but adding more shielding would make it too massive to get to mars in time given the alloted fuel. She would then have to build a more streamlined life support or maybe make it a robotic mission. After construction of the ship simple (don't want to tax the servers too much) simulations would be run on how the normal forces of space affect the craft along with random encounters such as meteor showers or solar storms (Probabilities of encounter could be determined by weather or not they are traveling through the asteroyed belt, the Kuiper belt, near the Sun, etc.).
These obstacles are fun just to think about, trying to figure it out in a game setting would make it everything that I wanted spore to be: free the imagination and just provide simple constraints for people to discover and overcome with there own ingenuity.
The other great appeal of this game would be the possibilities of exploration. Its one thing to see photos, artistic renditions or even videos of alien landscapes, but to actually explore them in a 3-D environment would be truly amazing.