Jump Gate mode
Currently after the players have built their base with some ships they have really nothing else to do in the game. To extend the gameplay I suggest the new Jump Gate mode with the following features:
1. Players on servers working in Jump Gate mode can build Jump Gates (only in space far from the planets) which must allow them to travel to other servers working in Jump Gate mode and meet other players.
2. The admin of the server should be able to independently reserve player slots for some predefined players (friends from Steam) and for players that may come from some other servers through Jump Gates.
3. The Jump Gate should be able to work in one of the two modes at any given time:
A. Random mode. In this mode the Gate sends the players to some random server working in Jump Gate mode which has enough free player slots for visitors from Jump Gates. The bigger the ship that tries to pass through the Gate in this mode the larger amount of energy the Gate should require. The target server may be chosen considering e. g. the location (the ping) and the language of the home server (preferences could be adjustable).
B. Targeted mode. In this mode the Gate sends the players to the specific server on which the players have built another Jump Gate which leads to their home server. If the Gate is offline or is destroyed on the one side the Gate on the other side must switch to Random mode. To function in Targeted Mode the Gate must require a pretty high amount of power so that it would be reasonable to keep it offline.
4. When starting the game in Jump Gate mode the players must be allowed to spawn only on planets' surfaces for the first time.
5. (Optional) The admin of the server must not be able to kick out the players who came from Jump Gates. I think this way it'll be more fun.
The main point of this suggestion is to create a long-term goal for the players: to be able to interact with other players they will have to build a ground base, get to space, accumulate enough resources and energy and finally build a Jump Gate and some large ship to explore what happens on other servers.