Learning scantling: design statement

[magwas]

(see Learning scantling, step 0: design flow
for context)
I have two examples in mind, so there are two design statements here.
I have made some modifications to the original idea though.

1. small catamaran
Purpose:
Small day-sailing catamaran for inland lakes and waterways (GL range V), hulls functioning as canoe. One crew and one passenger for catamaran configuration, one adult and one child for canoe configuration for each canoe. I actually intend to build it.
Design requirements:

• Should be small enough not to need certificate: LOA < 4.2m, sail area < 10m2
• The hulls should be useable themselves as canoe.
• Should be built from plywood.
• Should be suitable to be carried in cartop
• Marconi rig
• All parts and gears should be simple, cheaply and easily buildable or
• obtainable.

Owners description:
In holidays the family (two adults, two children) takes the boat on
cartop, and if there is a lake then sail it, if there is a river then
canoe.

2. 10m monohull sailboat
Purpose:
Blue water sailing cruiser in the 10m range. This is a working
example to have a boat which is within the applicable ranges for GL
scantling rules. I do not want to actually build it. If someone wants
something like that, I am open to change specification.
Owners description:
Retired couple wants to circumnavigate. They want to live in spartan circumstances, and extremely cost and environment conscious (read: I do not want to spend too much time with interior design as of yer). Visiting family is occasionaly taken for a daysail.
Design requirements:

• Special attention to be paid to structural strength and stability.
• Two masted schooner.
• One built from plywood and one from steel with origami method (I want to be able to design both).
• Good performance in light winds, safe in heavy seas.
• Trailerable according to EU rules ( beam < 2.5m, LOA < 12m, height < 4m)
• All parts and gears should be simple, cheaply and easily buildable or obtainable. (if possible)
• Should be easily handled by one crew (if possible).

Design options:
Electronics/nav station

• GPS (one builtin, one handheld for emergency use)
• autopilot
• electronic charts
• radar
• VHF radio
• AIS
• EPIRB (class I)
• SSB radio
• Pactor modem
• computer integrating all electronic navigational and communication gear. primary monitor in nav station desk, secondary in helm.
• spare computer
  
  Plumbing system:
• watermaker
• all taps with foot pump, primarily with sea water
• cold and hot fresh water for galley and shower
• one head/shower
• Galley:
• Stove and oven
• Sink
• Small space, to be easily operated in blue water conditions
  
  Propulsion
• Diesel engine: minimum safe HP

For both boats:
No measure of merit proposed.
Constraints are expressed as design requirements.
Warning about how changes affect the design process and pictures of other boats and options are omitted. I understand that they are very important for communication with the owner, but we don't have one here.

I guess the statement for the small boat is enough for such a small boat. It is?
With the cruising yacht I have a bad feeling about design options. I guess this is a part which should be thoroughly considered with a commercial design, because it affects a big chunk of budget. I also guess that (lack of) this part might cause the phenomenon of "unused boat in the backyard" at hobbyist. Hacking up the hull is considered nearly the end of the project but it isn't.

And the usual big question; is the above looks like a step in the right direction? Is there any conceptual problem or misunderstanding of some detail in the above?