What you could do is limit the amount of resources in each point rather than have it be time-based, and exo-shields would use some of that to run rather than just making the harvester produce at a reduced rate.
That's what I meant, as far as the time-based thing goes. I was just really talking about the volume of resources in there, since you can't draw down resources any faster than the main harvester rate. For the exo-shields, I don't see any reason to make it more complicated.
Although I also think that the resource harvest rate is a little high and am not sure about limiting it in this way. I'll play the game a bit more to see what I think of the balance in single player and then give you more input. My reaction is much like Admiral's: it's easy at this point to hit resource caps and have plenty of energy.
Well, fair enough. With the time limitation on the resources, plus the mercenaries, though, I think this will basically be resolved for the most part.
Edit: I should add that I think the mercenary ships idea is a good one and look forward to using it, but I view those ships as more of an extra and not a solution to the problem of having that abundance of resources in the first place.
I disagree -- the problem with the extra resources is not having anything to do with them. As long as you are not at your ship cap, resources are not that overdone. Once you are at your ship cap, they fly sky high. Now with mercenaries to round out your fleets, there's no good reason for ever having sky-high resources.
Usually smallish changes like this have a pretty huge effect on gameplay, so let's wait until some of the other changes in before really passing judgment there. I think the mercenaries will solve most of this except the imperative to expand, which the limitations on resources will solve.
A few things I've been thinking about in relation to this (and Rev, this might help with your comment about the command stations):
Right now, the knowledge you can get is limited per planet. I think that might also make sense for metal/crystal. Basically, the amount of available metal/crystal would be dependent on how many harvest points there are, but it would be drawn down as a single total per planet rather than per harvest point. So if one harvest point keeps getting destroyed, you can keep drawing down the total from others, just more slowly. AND, this would mean that the command stations themselves would also draw the resources down, so using the higher-level command stations would give you more resources but would deplete the planet's amount more quickly.
In the case of the home planets for players and AIs, those would have an extra-large amount of resources on them, perhaps enough to sustain everything on them for around 10-15 hours or so (assuming full burn rate the entire time). Thus it will really be a long time before you are running out of resources there, but it will happen eventually. Thus there is always the imperative to move forward and not waste your resources with tactics like entrenching and building a zillion overpriced mercenaries, etc.
With this model, I think I will also do away with the resource caps completely. If you want to amass 500 million metal, go for it. This basically makes it all more similar to knowledge. Otherwise the complexity of managing the economy and wondering if you are wasting finite resources is just too much. Also, I think that having the metal/crystal producer efficiency reductions would also be a thing of the past, since that too would be much too complex to try to manage in practice.
This has a few benefits, mostly simplicity and ease of management (and ease of review from the galaxy map), plus consistency with the knowledge model. But it also has the benefit of making planets as a whole only useful for a while, and not making the higher-level command stations so overpowered. In general, I think this would simplify a lot of the economy (no efficiency reductions, no way to make yourself permanently overpowered resource-wise with higher command stations), but at the same time increasing the longer-term strategic challenges. AI War is ideally placed for this sort of thing, due to the fact that it has such hugely longer games than any other.
My other idea is regarding the reinforcement levels. This is something that I think I will handle with a new special ship that the AI builds over time, and which the players can destroy to limit the AI through. I have not yet thought that all the way through, but I think it has a lot of potential to be very fun with letting players manage the amount of reinforcements the AI gets through a mechanic along the lines of datacenters.