Something ahistorical but should allow the player to have some control over what type of game they want to play.

Have a modifier in the initial game settings which will limit ratio of number and displacement of civilian shipping based upon the player fleet.  Maybe a "max number of civvie shipping lines" as well.

Having a ratio will make an inverse relationship on number of ships and size.  The higher the number of the ships, the less size they will be and vice versa, regardless of the values chosen.  It would be nice to be able to do this on a "per line" basis as an option to replicate large interstellar haulers and intra-system tramp freighters to both exist, though if that isn't doable, having the player choose between taking care of one or the other and the civilians covering the remainder will work.

For an easy example, let's take a "small" force of 100 ships totaling 1,000,000 tons, so if the player chooses 100% number and 100% displacement, the civilian shipping line(s) will default to having 100 ships massing 10,000 each, so a "jack of all, master of none" effect.  A 10%/100% choice would result in 10 ships at 100,000 each, so interstellar transport vibe, whilst a 100%/10% would be a small packet courier fleet of 1,000 ton ships.  This of course is based on averages, and allowing over 100% on either gives more options, but not necessary.

Just seems easier to mechanically tie it into what the player is doing than other mechanical subsytstems.  It will naturally provide a civilian shipping economy which reflects the player's own demands and "actions" in the ship economy and how that would trigger a civilian response.

Being honest, I like the way the civilian lines work now and like the experience you are describing Steve because it makes the growth of the empire feel organic to me.

That said, could we add some kind of mechanic where if a civilian ship sits idle for too long the line decommissions the ship? In game it can be explained as a company doesn't want to pay for maintenance of a ship that isn't doing anything. So if you want to decrease the number of ships you just mark a bunch of colonies as stable and wait for the ships to disappear.

 --- Perhaps give them a sort of fluff base? Like CMCs, they'll spring up on eligible worlds, but would serve as mock "supply bases". Having these tied to player colony sizes, pops, etc and making shipping lines rely on these outside of truly huge ships could give a lot of levers for both you the dev to balance with and you the player to interact with.

 --- Sorry for no effort post on this, I usually turn them off myself. XD

Interesting. Changing base carrying capacity of ships seems reckless. I can see it causing problems for the early game, which is already slow. Besides, all it really does is postpone what is already happening. Eventually, the civvies will just build more ships or larger ships and it all comes back again.

The maintenance idea seems good. A nice soft cap on individual potential. If I understood it correctly, it would only affect each line separately and so not cause problems with a growing empire, as new lines can simply pop up over time and fulfill that demand until they too become "decadent" and slow down growth to potentially nothing.

I think it is logical and appropriate that larger empires do things more massively and faster than smaller ones. Especially if compact in territory. It gives a sense of progress and allows the player to more easily marshall additional resources toward other interesting parts of the game. It provides a more or less clear transition between the early-game exploration phase where everything is slow; through the mid-game expansion phase where everything is fast; to the late-game exploitation phase where you can do anything you wish due to having infinite resources.

In my current campaign, I am 32 years into a conventional start and I have four shipping lines for the player race. The largest has forty-eight huge colony ships and forty-nine huge freighters, plus numerous smaller ones,  and seems to be building a new huge ship every few weeks. The other three shipping lines are considerably smaller.

The number of huge colony ships means that the civs will build up a new colony very quickly and also eat into source populations fairly quickly too.

So I am considering changing how shipping lines work, so they don't become so overwhelming, while trying to retain the flavour. I have a few ideas, such as halving the money received by civilian shipping, changing civilian designs so they are slower, significantly reducing the money for in-system transport, or maybe paying by distance travelled in km rather than transits made or limiting how often new ships can be built.

Another option is replacing dividends with a percentage maintenance payment, which is modified by an admin overhead that increases as the number of ships increases - effectively limiting the rate at which a shipping line can increase in size.

A more dramatic change would be altering transport for all ships, not just civilians, so less can be transported. That means fewer cargo points and less colonist capacity per ton.

However, I would like to hear other opinions and ideas before deciding how to tackle it.