I like the idea of incrementing food on a planet with more than one city. I do think all hubs should have better adjancencies than justuildings.

So I checked in a new update today based on further play testing.

Broadly speaking:

You can still build an unlimited number of cities but they now require 1 Promethion as well as food.  This way, you can try to block an enemy's population growth by keeping them from getting too much Promethion.

We removed the requirement for Promethion being needed for the research based imps but added Arnor Spice as a requirement for technology centric wonders.

The factories got a slight buff on the lower end (they do get quite powerful).

So the idea is that if you have access to lots of Promethion but not Durantium you can succeed by having a large population.  In the event you don't have much access to Promethion but do get Durantium, you can succeed via factories which enhance your population.

I kind of wish there was 1 more galactic resource tbh that I could use for Research.

Interesting. and because you can "Farm" Arnor spice with the right tech, that's a not a blocker. Sounds like it's a worthy option.

Heh, you could be mean and use antimatter for Research- that'd put a nice, hard choice between building all those ships with prototype engines, or with better missiles or the peaceful pursuit of science. 

One of my greatest gripes in 4x games is tech trees comprised of "techs" are just adding a % bonus to something existing. Maybe make more techs that "unlock" things (that aren't just simple buffs of existing things).

Also, I'd be a fan of build-able super-structures in space.

Also, gotta have SOME purpose to all those 0-class planets!

Limiting each planet to 2 cities will 'force' us to  build other improvements after we max out our population. This doesn't actually make Factories more desirable, but it does make Food and Morale less important.

We can calculate our manufacturing as:
( Construction + Raw Production ) * (1 +% Bonuses)

In the early game, increasing Construction and Raw Production will always be better, but once those numbers are high enough, then % Bonuses become very important.

For 3 Factories to be competitive with a City and 2 Farms, it needs to produce at least as much Construction as a City provides Raw Production.

I'd suggest 1 +0.5/Level Construction per Factory (The same as Space Elevators). This would give you 6 Construction from 3 Factories, which is not too overpowered compared to 4 Raw Production. This would also then make % bonuses more relevant because of higher Construction values. At some point, you will want those % bonuses, instead of more flat bonuses (assuming that the % bonuses are high enough).

Good ideas

Regarding cities/food why not tie this back to moral as it was in Galactic Civilizations II?  the more people you have the more entertainment buildings you need so no hard cap but, it limits itself by not having enough things to do to keep people happy?

Didn't  moral in Galciv 2 also affect research and construction, you need at least 80% moral to function normally?

Honestly, let's not mess with things too much in terms of the economy basics. I'm not a big fan of requiring arbitrary resources for anything other than special (i.e. Galactic or one-per-civ) buildings, as that produces really bad choke points that, while Humans can be good at compensating, AIs have a hard time with.

Our current problem seems to be that Population and Raw Production are 1:1.  That's linear growth, and it's extremely hard to beat that with anything in the way of well-balanced improvements.  Given that Raw Production provides broad power - it's the economy as a whole - anything that provides direct improvement to it has to be VERY carefully managed.

The old method was Sqrt(pop) = Raw Production.   It think that's too harsh, but a good non-linear association would probably be best.

I'd vote for Logrithmic association between population and production, using Log Base 2.  That means you get doublings of production at 2, 4, 8, 16, and 32 population.  It means that it's not a huge deal if a planet has 8 or 9 population, whereas right now that 1 additional pop can be VERY significant in production output.

I guess what I'm trying to say here is this:

I'd rather we balance things with futzing with % bonuses on individual improvements AFTER we've cut down on the effects that huge populations have.  I think it's easier to do that than other approaches such a limiting number of buildings or requiring resources. 

We (the community) can then embark on a blitz of bonus balancing attempts, to find the right mix for everything, safe in the knowledge that the base mechanic of pop:raw production is settled and we're not going to be facing a drastic change in the overall strategy model.

I think the main issue is that population is not that much different from building the specialized buildings, yes you need food and approval but those are just buildings as well.

So you have 1 farm 1 approval building and 1 city, what is the difference to 1 money, 1 factory and 1 research building? You can move numbers as much as you want, either it is redundant because both do the same or either specialized buildings or population is useless.

In Galciv2 you had taxes to balance approval, so it was operating on a different layer and felt different, but population and specialized buildings are just too similar.

Frog, are you arbitrarily going to cap city population? 

I only build a single city on planets anyway so it really does not affect me but will cities be 'upgradeable' so you can grow past the one population increase?

I see it like this:

Some have suggested a planet claiming sytem. I realise they are different games with different AI, but that system existed in at least one incarnation of Space Empires. It was terrible, and without going into too much detail, it resulted in all civs essentially claiming all planets in range, which in turn led to diplomatic madness, and made peace absolutely impossible, ever.  In GalCiv III it would mean '- - - You settled planets we claimed' for all about all, always, in every game.

Others have suggested a closed border system a la Sid Meier's Civilization. If this were implemented in the same way in GalCiv III, then it removes the influence culture-flip mechanic from the game - which is one way some players have their fun. It would also mean that boxing a civ in would be possible (as it is in Sid's Civ) - which is inconsistent with a game set in space.

I have no idea how difficult this would be to implement in terms of the current engine, but as a compromise, I would like to see something that hits the middle of both.

I am really not a fan of starbases and shipyards being able to be built, for example, next to a foreign empire's home planet, and by extension, in influence. Others are, I am not.

Non Influence Starbases, and Shipyards that end up in foreign influence, should flip, albeit a little slower, in a similar way to asteroid mines do currently. This would happen taking into account any anti/pro culture-flip modifiers. Maybe I'm wrong but AFAIK currently flipping shipyard and starbases is only possible through diplomatic purchase or Ideology tree, and only once?

Uncolonized, habitable planets that end up within civ influence inside an already colonized system would get a 'claimed' flag automatically. If there are any planets in the same system that are not in influence, then they are fair game.

Any planets in a neighbouring system where influence has spread, but that has no colonized planets would still be fair game and no 'claimed' flag would apply.

This would only apply to civs at peace. In war anything goes.

I DID make suggestions.

...Anyways, I'm ready to put this to the bygones.

Moving factories and laboratories to flat bonusses is key to balancing them vs cities (/asteroids). As a best practice I would even suggest this model:
 - all common improvements only provide flat bonusses.
 - all colony uniques provide percentage general bonus and a flat bonus from taken adjacency.
 - player and galaxy uniques provide percentages and/or empire wide percentages.
 - citizens provide percentages
 - exploration age techs provide flat bonusses
 - other techs provide percentages

This begs the question about what will happen to the space elevator. I would tweak above proposal to this:

Basic Factory (BF): 1.5 + .25/level giving 1 adjacency
and
Space Elevator (SE): 20% + .25/level giving 2 adjacency

for a 3 BF triangle this adds up to 6 manufacturingin both categories.
for a 2 BF+SE triangle this adds up to 5 manufacturing and +20%

Keep in mind, that there is a dynamic balance between flat and percent bonusses. Suppose you get to choose between +1 flat manufacturing and +10% manufacturing If you have 15 flat manufacturing allready, you gain more from adding +10%. If you have two workers on this world allready (+60%) the +10% still only add one manufacturing, but the +1 adds +1.6 due to the workers and is better again.

Let's talk about population: Keep the model mostly as it is now (people hate seeing numbers of things they use to play go down more than seeing numbers of things they don't play go up). Population is interconnected with some many other balance aspects, it is virtually impossible to change it without unbalancing something.

But I would suggest the following balance modification for synthetics:

base pop cap: 10
approval can stay at 100
popcap is increased via technologies:
 - up to 15 within age of exploration
 - up to 25 within age of war
 - up to 40 within third age
 - up to 100 after that

It's probably not perfect, but it's an economical stepping stone towards finding the right numbers for synthetics regardless on whether it will be completely tech absed or improvement based in the end.