Before I get to my idea, I just want to say that I put a lot of thought into this. Also remember that, if you think this is too complicated, that this idea can always be simplified, and likely will be simplified, if it ever is implemented. I also am not suggesting that the space resources be removed, unless, of course, Stardock wants to go that route.
At its simplest form, my idea is to add tradable resources on planets. Of course it is more complex than that, so please bear with me.
This idea was initially inspired by the resource system in Civilization IV. In that game, you can claim recourses that give you bonuses or allow you to build certain units, and these resources are tradable. I should make clear that I have no intention of suggesting a direct clone of the Civilization IV resource system. (I will explain more later)
These resources will be located on planets, instead of in space. They would appear not just on habitable planets, but also on class 0 planets, finally giving them some usefulness. Resources on habitable planets are obtained by colonizing them, while those on class 0 planets can be hooked up with a space miner (or a new unit, if you so desire, although I personally prefer the space miner option). If you want to make things more interesting, you can have class 0 planets also have different environments, and these planets cannot be mined until you have the basic colonization tech. (For this system to work most effectively, the game needs to distinguish between rocky and gas planets)
Once you have one these resources, they will do one of a variety of things. The most interesting would be weapon resources, which allows you to research and use better weapons. Unlike oil in Civilization IV, there should not be a be-all end-all resource. Each resource is tied to a specific side-branch located along one of the main weapon technology lines. (They would not branch out at the beginning of the tech tree. At the earliest, they would branch our after plasma weapons, harpoon, and singularity drivers. The final locations would have to be determined through lots of testing and would undergo a lot of corrections for balance) These weapons are more significantly expensive to research and build, but also do more damage. If you do not have the needed resources, you can still research up the main tech lines. Since these weapons are much cheaper to research and build, a skilled player can still compete militarily by out researching or out producing his or her opponents.
There are other resources that can do a large number of other things. Some can unlock certain buildings, increase stats (like the space resources). If the game makes the distinction between gas and rocky planets, there can be resources that can only be found on gas giants. Let your imagination run wild! The main idea, though, is that there should be no one resource that you MUST have. They should be carefully balanced so it is still possible to win even if you have no resources at all, in the same way it is possible to win without any of the space resources we have right know: it is difficult and undesirable, but it can be done.
Another idea is that, like in Civilization IV, some of these resources are not visible until you research a certain technology. This would especially be true of weapons technologies. Essentially, when the resource becomes visible represents when that civilization realizes that resource has value. In addition, these resources could stack, increasing in effect the more you have. With weapon and building resources, the weapon or building connected to the resource will be cheaper to research and build. Of course, if this is too complex, both of these ideas can be scraped.
If you loose a resource, you loose any stat-boosting effects, and can no longer build or research anything connected to that resource. However, anything you already built (ships, buildings, ext.) will work as normal)
Another major point of my idea is that these resources should be tradable, which can open up some interesting dynamics. Most importantly, these resources these resources should be rare enough that it is simply impossible to have them all without trading. Some resources, like the weapon-related resources, would be impossible to obtain. Unless you are close/in an alliance, and even then it is very expensive. In addition, trading resources, especially weapon-related resources, with a civ will anger that civ’s enemies, and will result in a drop in relations.
It would take a lot of work with the AI to get the trading system working without making it an exploit. This is one of the reasons I do not expect to see anything remotely similar to this until at least Gal Civ 3. But I think it will add some interesting dynamics to the game.
I would like to hear you’re thought on this. Especially, I would like to hear your ideas on additional resource effects. Remember, however, that this idea can always be simplified as desired, so please don’t simply complain about how this is "too complicated." Tell me how you want to see this simplified. I want to know.