a)
If speed is your primary goal, I think you might benefit from looking at some
catamaran designs.
Long and narrow hulls help avoid parasitic drag... up to a point.
Unfortunately, speed tends to come with a decrease in cargo capacity... the opposite of the cruising ideal.
Of course, a sustained powered sprint consumes limited/precious petroleum-based
fuel, so there is that.
b)
For a sustained 18-knots, I like the Dashew-designed 115' power-boat.
Although the
single functioning example is stretched to 130', the duration is in the neighborhood of 4-5,000 miles with multiple fridges and freezers, so it certainly fits the 'cruising' definition.
Another plus for this design:
* it is engineered with massively over-built doors and windows to survive a 'hundred-year sneaker wave'.
Undesirable boarders would probably get tired of banging on stuff as they watch their home-port shrink in the rear-view.
c)
I trained with some phenomenal Martial Artists.
All recommend being someplace else instead of going to battle.
And yet, pirates can drop by in Noplace
Alaska as well as downtown Detroit or
Baltimore.