Station | Outpost Planet

Colony | Colonized Planet

Society | Socialized Planet

Province | Provincial Planet

Capitol | Capitol planet

Or:

Outpost / Station

Colony

District Planet

Integrated Planet

Imperialized Planet

Also, depending on what you want to convey, Ecumenopolis means 'planet-wide city' (like Trantor or Coruscant, depending on your choice of geekdom. ).

I personally use:

- Outpost

- Colony

- Production Center

- Metropolis

- Capitol

but these may not apply perfectly to your particular game?

I would say it's all a process of colonization, once people start settling. More specific terms to indicate the state of the planet and it's capabilities may be more useful.

-Possession (Held territory without a permanent presence)

-Outpost (Minimal Permanent manned presence)

-Mandate (The beginnings of a colony, where there has been a mandate to settle the region)

-Dependency (A start up colony that's still dependent on the mother nation for essentials)

-Protectorate (A colony that is self sufficient, except for in terms of military defenses)

-Stronghold (A colony that has achieved self-defensive capabilities)

-Capital (A fully developed world that can also colonize and protect others, capable of serving as the center of your empire in that region)

• Outpost
• Station
• Colony
• Occupied world
• Citadel world

• Minor station
• Major station
• Minor colony
• Major colony
• Minor world
• Major world

• Outpost planet
• Station planet
• Colonized planet
• Established planet
• Capitalized planet

What about telling us where you currently stand, and what you don't like about it? What are the benefits that each level brings?

We're kinda shooting in the dark here!

How many capitals are there in the United States?

So you're actually looking for two separate 'grades'.

One is the distance from the core

One that is the current population/administration state of the planet

You may even want a third grade, just for ambience, stating the physical size of the planet. It doesn't even need to affect the gameplay.

Then you mix them together to form the actual title, or else display them separately.

"[status] [location] planet" or "[status] [location] [size-name]"

"Occupied frontier planet"

"Settled core planet"

I suggest:

Size grade:

• minor ____ planet (minor [fringe] planet), alternatively, "______ planetoid"
• ____ planet
• ____ world

Occupation grade:

• Posted / Stationed / Depot)
• Settled
• Colonized
• Established
• Bureaucratic
• Administrated
• Imperial Capital

Is the 'location' grade supposed to be the fringes of your empire, or the fringes of the galaxy? Naming differs between the two.

Location grade: (if galactic fringe)

- Fringe planet

- Distant planet

- Planet (just planet)

- Inner planet

- Core planet

Location grade: (if your empire's fringe)

- Frontier planet

- Border planet

- Provincial planet

- Planet (just planet)

- Central planet

This gives you things like:

Colonized minor provincial planet (alternatively, Colonized provincial planetoid)

Established border world

Administrated fringe planet

This is incredibly simple to code, adds alot to the ambience, and (I think) satisfies your requirements.

You can even use similar techniques (with more complex generation rules, but still not complex to code) to generate flavor text descriptions of planets.

• Depot - Totally or nearly unmanned location. Only serves as an extention of your realm. You do not technically own it, but for the purposes of internal economy system, the game considers this place as a part of your connected realm. Basically a shortcut through uncolonized stars without colonizing anything and costing little at the same time. Then again anyone can take that location away by simply building a settlement of the next level of settlement there. Also, depots of several non-hostile countries could exists on the same planet at the same time.
• Permanent settlement - A location that is permanently inhabited, It can be anything to one village to the capital.

Now, the sub-divisions of the permanent settlement:

• Expedition - a very small handful of people, who are dependant on the upkeep of the empire. Does not contain enough people to sustain a permanent self growing location without immigration. Population growth done though the voluntary travel of people to there. Or as a deportation location, where people are sent without their concent and have do by with whatever they have been given. State funded professional base building. Science expedition? Enterprenour expedition? Military expedition? Could used to assess the local resources.
• Enclave - can sustain itself without immigration and supplies. Starts to create output of its most abundant resource.
• Settlement - most of the important strategic locations are secured and no other empire can no longer do their stuff here without military action.
• Colony - this place is through its birth pains and is starting to do, what the original designation was. Is offically a part of the empire.
• World - a working economy. Not a strain on the system. Entirely integrated into your empire. Considerable population. A core world one would say.
• ...-center - a center of its designation. Your capital would be Administrative-center. Your world with the biggest trading world would be Trade-center. And so on.