So, first forces up for expansion in my mind are
I say this because their ships are the most readily available in my eyes. Visit these links for examples.
I would create an expansion by writing the rules for ships, attributing points costs to ships and captains individually and treating the models from the Dreadfleet boxed set as "Special Characters."
The new ships would be weaker than the overpowered Dreadfleet boats. Things like cogs and special character captains (like Jaego Roth, Aranessa Saltspite etc.) would cost extra.
Has the potential to be a fun little project. Any thoughts?