Schnellboot, aka as an E-boat? Na, Vosper MTB for this ol' cat, being British. Preferably, the late-war four-tube one. Make the freighter a Liberty Ship or maybe even model an Armed Merchant Cruiser (AMC, aka 'Admiralty-Made Coffin') such as the gallant 
Jervis Bay  and have fun chasing the German 
Atlantis or stopping and sinking a Maru.
Love the perkies-for-ship idea. Save up 200 for a 'Town' Class four-stacker, 
Campbeltown  (ex-U.S.S. 
Buchanan) preferred, 400 for a Tribal.
Yohoho and a bottle of rum . . . 
