If we can port SHIII ships, then we should easily be able to kitbash ships from SHIV models and import entirely new ones as well.

Eventually, at least.
Of the merchants ships in SHIII, some are already in the game and some are higher priority than others. If I list a ship that actually is in SHIV, then I apologize - I don't have a copy yet and am going by the reports of others.
Already in SHIV:
Troop Transport (NTR)
LST
T3 Tanker
Fishing Boat.
Trawler.
Tugboat.
Victory.
Liberty.
Higher Priority:
- Coastal Merchant.
- Small Merchant.
- Small Tanker.
- Sergbuto's NPTR clone.
- Sergbuto's NKGN clone.
- Small Coastal Vessel.
Lower Priority:
- Passenger Liner - too modern looking.
- C2 and C3 - I guess we could convert these, but I was hoping to never have to look at them again.:p
- T2 - Poor quality model.
Not sure what British warships are already in SHIV, but all stock US ones seem to be, except the J.C. Butler class (which we could add).
There might be some new SHIII models which could be imported as well, and maybe a few kitbashes (if we are allowed to import those) - although some of my merchants aren't really high enough quality for this game (maybe the Whale Factory and the Pyro would work). Iambecomelife's would definitely look good though.:hmm: