Personally, I'd want it made from the Virtual Skipper 3 (or the next installment coming out soon) Engine.
Cause it has windirection and currents modelled, which I don't think SH3 had them as they should be. ie there is wind direction, but it doesn't effect waves and the boat etc and there sure as hell isn't water currents.
I have actually got VS3, not a bad game, but I waish it had the world mapped like SH3 instead of just regional ares of auckland, scotland etc
Have to have a look at the next installment and see if if has the ability to round-the-world sail.
Basically I would think adding weapons etc in the engine is easier than currents etc, plus they have modelled crew and are animated, doing the rigging etc
My 2c