While I messaged alex on twitter with this thought, I figure it should be brought here too;
Been discussing an idea for cryosleeper ships on the unofficial discord with Tarn#5882 who suggested they could allow for size 7+ colonies.
It seemed like a neat idea? Maybe even go as far as designating one world as the benefactor regardless of proximity to the sleepers?
I feel this would also be a comfortable lore reasoning for you having one colony with a population in the higher numbers. You found something monumentally important after all, a cryo ship discovery should be a sector-shaking event. Having it be able to "aim" at the colony you want to become your new homeworld would be an added bonus to its existing features that doesn't force the player to find the cryoship first, as your established colonies far away might not benefit directly, but at least one world will become your new capital.
With all the benefits and all the problems it will cause. After all, never forget, you are the upstart in the sector. The factions might not like you having access to that ship and its people...