While I am suggesting a significant increase in speed, it is still a fraction of the speed of cargo ships.
Currently cargo ships have a speed of 60:
While Freighters have a speed of 3:
I am proposing increasing the speed of Freighters to 20.
Instead of only being 5% of the speed of Cargo/Trade ships, this would make them 33% the speed of them.
This leaves Cargo/Trade Ships still significantly faster and makes Freighters far more practical to use for things beyond same island resource transfers and make them useful in the Trading Post, as well.
This would still leave them as the slowest ship, with the same speed as a Balloon Carrier.