Apologies for double post, but I also have a suggestion which I think should be separated from the above discussion:
Currently, a number of quantities which scale with starting population at game start have hard limits beyond which they do not scale. The most obvious of these is research points and research labs which are both capped at 200,000 and 50 respectively (corresponding to 1.25b population). Similarly the number of starting officers is capped at, IIRC, 200 (where the default is 150 officers at 500m pop) which tends to be not enough at high populations with a lot of free BPs.
I would suggest that these and any other hard caps are removed and the scaling with population is directly proportional for all populations, possibly with a minimum for very low-pop starts.
While it is trivial for the player to change these quantities at game start, the bigger issue in my mind is the NPR balance. Additionally I think removing particularly the 50 Labs hard cap would help generated NPRs in the later game period remain competitive, as right now it is possible for the player to easily exceed the generated NPR starting tech levels once they have 75 or 100 labs and a few levels of RP boosting tech since new NPRs are still limited to 50 labs on spawning.
Of course players may still want to do e.g. 8b pop starts and the like, for which NPRs starting with 1.28 million RP might be a bit excessive, but I think it is best to enable the NPRs to scale effectively under a wide range of conditions and then trust the player to adjust the start as needed to reach their preferred balance (i.e., by starting with a smaller population and manually scaling up as desired themselves).