It may not matter since everything was supposedly changed in a manner that should have canceled out any negative effects due to the changes, but I am curious how much (or how little) capping the growth of player colonies to size 6 limits total colony income due to population size...
Typically a single size 6 world dedicated to profit (i.e. Commerce, exploration goodies, story point improvements, 3 other credit making industries, lots of alpha cores) is generally pulling in 500,000 credits or more profit per month for me, across a number of both modded and unmodded games. This is as you note, assuming I don't own all other worlds. The more you own, the less income per planet you tend to get, which accelerates once you have a good fraction of all planets.
To be honest, one or two worlds like that and you're essentially set for the rest of the game in regards to credits, so I don't think the population cap has harmed end game any.
However, more to the topic, what I'm describing is the very end point of a colony's life cycle. To get there takes time, credits and a fleet capable of tackling end game threats. Growth is slow, especially on high hazard worlds, and to offset that you spend lots of credits every month. Size 6 without a Cryosleeper in system or nearby takes a long, long time. In addition to reach that level of profit also takes a bunch of alpha cores plus exploration. Generally you'll have an end game fleet and be doing end game things long before your colonies reach size 6.
I'll agree with the earlier statement that accessibility is the key statistic for colonies, which is why my first story point investment on any planet is to improve the space port and bump accessibility by 20%. It increases profit, growth, and ability to import needed goods if base accessibility is low. Similarly, Megaport and Waystation are expensive to build initially, but are necessary for maximum profitability.
In reality, colonies are credit sinks for most of the game. Just think about the costs associated with a fully upgraded colony - Commerce, Free port, and sufficient stability.
1.75 Million for the star fortress and it's +3 stability. 450k for Ground Defenses and Patrol HQ for another +2 stability. 400k for Megaport and Waystation for +40% accessibility. Even the cheapest Terran world running farming, mining and light industry is another 400k. Lastly 450k for Commerce.
That's 3.45 million in just industries for a single planet, not including monthly hazard pay, or the credit value you could get from selling exploration goodies or alpha cores. My latest run's 661k profitable colony is using 6 alpha cores, 6 beta cores, and 3 colony goodies worth another 3.5 million.
For reference, if I pull all those goodies and cores off (leaving the Alpha core administrator in place), the profit drops from 661k to 286k, although that still has story improvements to Megaport, Mining and Commerce. This is with a colony system literally at the bottom right corner of the map. Something like a -35% accessibility penalty for distance - but was worth it to me because of the presence of a cryosleeper and a gate in system.
