Thing is, does it make enough of a difference before trade/refineries become the dominant form of income?
Early game, tax and extractor income is dominant. Unless you're in the pocket and can go all-out eco, at very best you'll get a modest boost out of trade/refineries. It will NOT make up the majority of your income by any means.
An alternate idea might be free population UPGRADE?
Too similar to the Progen's colonize, which offers a generic discount to all planet upgrades. We need to at this from a different angle to keep the abilities different.
free additional logistics and/or tactical slots, or free logistics/tactical upgrades?
Can't be permanent. There is only one capital ship ability in the entire game whose effects are permanent, and that's a highly situational ultimate.