Wow, designing a multi-player (server) game is quite the challenge but I'm really starting to "see" how it will all come together. Here's what I'm seeing, at this (early) stage:
Skyport-Alpha will be a 2-6 player, server based space simulation game. You will trade, explore and/or transport around a vast universe with both friendly and hostile alien environments. Not unlike both Elite Dangerous and RSI: Star Citizen (both of which we backed on kickstarter), Skyport-Alpha will be a space trader type game however it will not be an MMO, perhaps a new breed of Small Local Network Game (SLNG).
We will use Unity3D for development for numerous reasons one being it will allow us to offer a "lite" (free) version where the server can be run in a browser window (limited save/galaxy size).
Some of the early design we are working on now are seeming simple thing like launching the server, creating accounts and then connecting with the clients. To allow single player games we may have to develop a process to run the server inside the single player game, or simply run the server on the same computer.