Thank you for making this mod, and for spending the last 2 years supporting it! I have only used this for my last 2 playthroughs but already I am in love with it. I don't know what I'd do without Astropolis and Siphon stations and use them everywhere. Siphon stations in particular have consistently been the wealthiest and fastest-growing colonies I've been able to make with an otherwise mostly vanilla game. I wouldn't say that it's overpowered, but they certainly have a few advantages over traditional colonies which make them very strong with a number of colony items. In particular:
Synchrotron Core: stations don't count as having an atmosphere, so can be used
Nanoforge: stations don't count as habitable, so they don't have a polluting effect
Plasma Dynamo: siphon stations count as being on a gas giant, so this is super effective on siphon stations
Catalytic Core: same as Synchrotron core, stations don't have an atmosphere
The thing that makes stations so profitable is their inherent 100% hazard rating. Finding a good Uninhabitable, No-Atmosphere planet to use nanoforges and other items comes with tradeoffs depending on the hazard rating and where it is in relation to other colonies. But being able to poop out an immensely profitable station with great 100% hazard rating in any system I want makes colonizing Barren/no atmosphere worlds much less useful. I don't know if the effect is strong enough to count as unbalanced but making a Siphon station produce 3-400,000 credits a month is, if nothing else, very straightforward and not as RNG-dependent as finding a suitably low-hazard world to colonize.
I think building a station should be way more materials-intensive, especially given how profitable they are. I get that the resources required to make a station are proportional to founding a planetary colony, but the planetary colony would have tons of raw materials on the planet itself to bootstrap with whereas every kilo of material that goes into building the station has to be shipped there. 1000 metals and 250 transplutonics is chump change! I think players should either be required to provide 10x as much metals and transplutonics to build the station in the first place and/or that stations should have a constant demand for these items which grows as it grows.
Stations can definitely produce a lot of income, but by the time stations can be used to generate lots of money, the player will already be high level and very rich, and have lots of options for making money quickly. They're not something that can be exploited early on to get money easily.
Also, it's not beneficial for the player to only use stations - they still need food and Domain-era artifacts from planetary markets. Overall, I think station balance is in a good place because it makes sense to build some of them, but they're not strictly better than planetary markets and the player needs to already be rich and powerful to exploit them to the maximum extent with special items.
On a completely unrelated note, I figured out that it's possible to build mining stations directly on top of a hyperspace entry/exit point if the hyperspace entry point has an asteroid field around it. If you have a size 6 mining station with a star fortress on top of a hyperspace entry point, every hostile fleet is basically instantly destroyed when they warp into the system. The effect only happens if you're physically present in the system, but since the star fortress is right on top of the entry point every hostile fleet is immediately forced into combat with it and any fleets around the colony. I colonized a nebula with a single hyperspace entry point and if I'm in the system it cannot be invaded or raided by anyone. Is this intentional? Because it certainly is hilarious!
I wasn't previously aware of this interaction! It doesn't seem all that imbalanced since a huge Nex invasion fleet should still be able to defeat it without player intervention.
Have you tested this on a long time scale? Theoretically the player shouldn't be able to line up the station's orbit perfectly with the jump point, and over several months it should drift away.
I could prevent this from occurring by blocking construction on top of jump points, but it seems pretty realistic to build fortifications/settlements at choke points and try to leverage that.
