As to the purpose of the ships:
For each station and planet, you also include a value, ValueX. (Name to be determined. It basically represents civilian happiness: luxury, connections to the outside world, visits from family members, etc.) ValueX slowly degrades over time, with the degradation rate increasing based on the size of the population. When ValueX falls below 67%, your station's productivity begins to decline, starting with 100% productivity at 67% and ending at 0% productivity at 0%. (All arbitrary, changeable values). When ValueX falls below 33%, your population begins to leave (at a slow rate, starting slowly at 33% and increasing the rate of disappearance as it approaches 0%).
I was re-reading some of this and I had an idea I might suggest. Once the level is low enough to facilitate or trigger the population decline, that it would only go so far before reaching a new equilibrium, that over time may start going down again, or rise depending on circumstances. If I understand the original idea, once the decline started, it would just keep going unless you took direct action.
Since irl it would be based on the supply of resources etc for a given population, once that population got lowered to a certain amount, the available resources would be enough to satisfy the remaining population. That way, it would at least slow down the population drop and do it kind of in stages with plateaus of stability for a while.
Just a thought.
Also, embargoes vs sieges. You could embargo a planet and prevent goods from being sent and cause a slower attrition of population, while a siege would cause an immediate outpouring of civilians rather than a slow drop in population.
So you could drive down a planets population if you wanted, by hindering their ability to get goods, provided you were the one supplying a large chunk of their trade, or by just shooting the crap out of anything that was trying to supply them, with the natural consequences of those actions of course.
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