It should be possible to upgrade any ship for GS into a premium ship with all the bonus traits:
-no repairs
- +2 cargo slots
-generates 20% free synergy
- +credits
A neat additional bonus would be, if the ship would also be promoted to the highest rank of the tier it’s in (an r4 ship would become r6 with all the upgrades/additional slots the higher rank has: bit more hull, bit more shield, bit faster etc).
The reason for this suggestion is, that it’s fun to fly a destroyer but with my Mammoth i get way more out of a match/mission and that’s a shame. Also it gives people a choice what kind of internals they want on their premium ship. Upgrade T-Rex or buy Mammoth for example