normaly its 1-2 ships per major content patch and remember Essex got implemented in a hotfix and hasnt even mensioned in the patch notes
i dont know release dates but yeah this could work:
1 First Rate
1 2nd Rate
3 3rd Rates
3 4 th Rates
6 5 th Rates
1 6 th Rate
2 Traders
and creating a 3d models is only 20-25% of the work geting one ship ingame.