Usually simple is better, therefore I suggest a mechanic that will help limit taking planets, while still giving the air of freedom of expansion.
First, we have a research tree that can be researched up to 30 planets that can be taken without the effects of corruption (as long as they are within 150 LY of your Capital). After this, every planet you take incurs corruption. There are 3 factors to determining the total corruption felt by that planet.
A flat -1 happiness for every colony past 30.
Taking a -0.1 to happiness per 10 LY away from your stating position, known as your Capital (If you lose your Capital, your Capital reverts to your nearest planet and your entire empire is recalculated based on that).
Taking into account the size of the planet you wish to take: Starting at 14K Km being neutral, you gain or remove .1 corruption per 1K Km above or below 14K Km. Example, if you have a 5k km planet you would adjust corruption by adding a +0.9 vs a 23k km planet adding a -0.8 additional corruption.
This allows both size of the planet and the distance from your Capital to reflect just how bad the corruption is on that planet. It means at a certain distance its just isn’t feasible to try and colonize or take a planet. This also make smaller planets more strategic and gives them more value.
I also want to add 3 more rules about corruption.
- Corruption doesn’t just have an effect on happiness, but it also increases the time it takes to build a single building or ship on that planet. For every -0.1 corruption you increase the base build times by 10% (this isn’t negated by positive desirability buildings).
If you try to take a large planet 300 LY away, that is a large planet, that would be -4.5 corruption, which would increase the base build times by 450% (that is around an hour for your 12 min buildings). Even if you brought the resources, the people, and the money, because you are so far away from your supply lines it takes much longer to organize and build buildings, as well as the level of corruption among the colonists and leadership taking bribes and generally slowing construction.
This hinders your ability to keep a hold of that planet, takes much longer to be productive, and its much hard to establish a military foothold that far out from your main area.
When you take an enemy planet it incurs a -1 corruption modifier for 24 hours after its taken. This represents over reach, rebellions, bribes, kick backs, terrorism, and other negative effects a conquered people deal with as they readjust.
Down below I am suggesting bring in Upkeep for planets, within this, I am suggesting that corruption again be a multiplier for Upkeep. You are 300 LY away, you have to pay 400% increase in upkeep of all buildings. This means that you will have a hard time producing an industry far away from your Capital, however you can still make the tactical solution of paying all that extra upkeep for a strategic placement.
Now, this probably means people will be able to take 50-100 planets nearby, while still being able to take some planets at a distance. However The limitations really make it hard to get to that 200-300+ (sometimes 400-700) planet count that we had back in A2.
To add a bit more depth and to use up pools of resources, I am also suggesting that we have a very small amount of upkeep attached to each building.
What about Syntis? I actually think that Syntis should do away with research only options and limitations and adopt corruption. The reality of our scifi situation here is that even Syntis would deal with some kind of eroding factors. Instead of calling it Corruption, we can call it Interference.
Interference works exactly like Corruption, however Syntis can deal with it slightly different with slightly different effects. Syntis can use Signal Boosters on their planets, but since they don’t deal with happiness, these boosters will be EXTREMELY expensive in population, resources, and credits. This reflects the cost of multiple happiness centers vs a few Signal Boosters.
Secondly, instead of increasing the time it takes to build farther away, Syntis internal processing units malfunction decreasing their growth factor based on temperature and land mass to water ratio. This means instead of taking huge amounts of time to get started and maintain a colony like organics, Syntis have to throw population at sustaining a colony until the point where they actually can maintain growth (which will be minimal), requiring Syntis to maintain better supply lines of population to maintain their outer colonies.
OK OK OK FLEETS
Honestly, this is even more simple.
Upkeep based on the hull of the ship,
Then once you start getting bigger and bigger that upkeep on ships starts to increase. For every single planet past your 30 free planets, upkeep increases on all ships by 2%. I also suggestion using @DeicidE suggestion, and have upkeep reduced by 25% for all ships inside of a fleet, and a further reduction of 25% if the fleet is stationed in the planet orbit as a shipyard*.
*The shipyard has to have access to the same tier of the highest tier ship in that fleet for this to successfully give the reduction.
What do you all think?