I've finished the economy framework! Now I just need to create UI for it...
Here's what I have done so far:
Population now consumes resources, and their growth/decline is based on the available resources. If there's a shortage, then all population that consumes that resource suffers from the shortage.
The growth formula is as following:
Growth/Decline = population count * 0.05 * (shortage - (Space Usage / Total Space))
The value for shortage is calculated as follows: Total available resource / Total resource consumption. So if you have 100 food, but 200 population, the shortage is 0.5.
The value for Space Usage is total population space usage on the planet's climate type, while Total Space is number of regions multiplied by 10. If a race's space usage is 1, then that race can have 10 units of population per region. It accounts for multiple races (it tallies them all up)
So if you have 0.5 shortage, and the planet is half-full, then there's no growth or decline. Nifty, isn't it? It's possible to have two races, one starving and one prospering if both consumes different resources (Ores for one, food for other)
I've also decided that instead of having the game automatically scrap items and potentially causing frustration for players (Dude, where's my scout? syndrome), the game will simply prevent the player from ending his turn if maintenance costs exceeds the available resources. Then the user can click on financial information and have a list of ships and buildings that consumes that resource so he can scrap any of them from this screen. This will make things a lot more simple both in front-end and under the hood!
The empire also now stores resources, or if they are not storable, converts them into a storable resource. Regions now produce and consume resources. Everything's there, just need the UI...