Ok, I am new player of GC3 (which I like) and a fairly seasoned player of the Civilzation series (started on civ 1 when I was 9 
. Have played a few other Stardock's 4x.
Many players recognize that today, there is no "strategic choice" around expansion / mass planet spamming. You should just go for it. A 4x gets cool when you are confronted with tough strategic decision (going tall vs. wide / rushing cool techs vs. taking the time to build some defense in case you get attacked / eXploring or building buildings...)
In GC3, when you settle a planet you first get the "normal benefit" (like any 4x):
- you block a spot: it is yours and no one can settle it after
- you open an "opportunity" to get long term benefits (research, prod...) once your city is built a bit taller
- you get influence / zone of control / expand borders
But you ALSO get HUGE benefits which are specific to this game:
- it expands your ship range. Suddenly your whole fleet around the galaxy can travel there, even with no life support -> get access to new eXploration opportunities / strategic ressources. This gives the massive advantage to meet more civilization with whom you get nice trades (tech...)
- you get ideology points (and unless you have zealots, 99% of your ideology points will come from there. The +0.1 / 0.2 buildings dont do much). Idealogy points gives cool benefits
- smaller impact: you get immediately some luxury stuff (which you can trade or simply get benefit from). Maybe you should have to build a small low cost building to obtain them
(I probably missed other stuff, sorry I am new
Also, the way planetary invasion work: enemies cannot attack you very early. No need to defend at the start.
And the cost for expanding is very small, at least compared to civilization and most 4x
- buying or building a colony ship does not cost much. You can buy at game starts and get easy money from trades. It is not a constraint resource (at Civ, you have less money so buying the first settler is not in the early game ; others get easier).
- it cost you some population. That is a very interesting feature. However the population is not lost, just transfered. Also, given how population works, having 2 small planets (the one who built the colony ship and the newly founded one) will create more population per turn that having a bigger one (sorry if I am wrong
- Usually, in a 4x a settler / colony ship is very fragile. You only let it travel alone if you are 200% sure that there are no barbarians / ennemies nearby. Here I fell that it is not an issue. If you are unsure of the area you fly, you just keep one movement point to retreat if you have a bad encounters. Hence, no need to escort -> you save money compared to most 4x
Suggestion of ways to mitigate this:
1) I love the population cost. Maybe you should "loose" 2 population units when the planet is settled (makes sense: not easy to colonise a new planet). So colony ships could contain 3-5 population at start, then transfering 1-3 to new planets
1) 1 bis: colony ships could cost more money / production time to be built
2) The exponent on the population does give an advantage to go tall rather than wide. But early game, you still have the issue that 2 planets make more babies than one. So it is worth to eXpand agressively. Maybe for the first 20 turns, a new planet should have lower population growth rate.
3) Happiness / morale is the classical way to balance wide strategies. In most 4x, you cannot expand too fast compared to your tech tree (which unlocks hapiness buildings). Here, the idea is present, but you need to tweak the variable a bit to make it more painful. In Civ, below -10 happiness, it gets messy, even for an ICS strategy.
4) Ideology: maybe you should also get it from going tall rather than wide ? Once you have settled your e.g. 10 planets, you know that you wont get much ideology anymore. It's a bit sad. Maybe a few buildings / trigger events in tall cities could give more ideology. (to balance the fact that otherwise, only going wide gets you mass ideology)
5) The range expansion on all your ship has a massive impact (given that meeting new civs is a huge source of income due to tech trade, hence a source of buying new ships). Maybe new colonies should only give low range during the first e.g. 20 turns
6) Maintenance cost should also be painful at the start to make zero income planets a bit less appealing. But for me, in a sense, this maintenance burden shall already be included in the cost ob building / buy the ship. No need to add complexity
7) you can regroup item 2 and item 5 (tbd 6) by calling a new colony an outpost (idea come from another post), which lasts like 20 turns. Outpust has lower population growth, give less ship range (and tbd has a maintenance burden)
8) adress the "no need for escort". Pirates should be faster to have a chance to get them. (and maybe they would really focus those and avoid e.g. scout)
9) planetary invasion should be done earlier ? so that you actually want to defend and not just ICS ?
What do you think ? Vote for the best mitigant and have the Devs implement it ! Personnaly, I would go for all of the above (except 6 and 9 ; on 6, the more general topic, already debated is to make maintenance cost / income in general more important ; currently, beeing in positive or negative in GPT has very little impact compared to e.g. trading techs)
Abbadon
