Mark,
There are designs already out there both with a normally stayed mast and the ugly things above the deck to hold
the mast up.

Not much point in doing anything unless it makes a difference.
So yes the unstayed mast does restrict the rig that can go on the boat.
The advantage comes in simplicity and speed of rigging along with good asthetics. Nothing on the market today that has all 3.

So far current designs are not making that much of an impression in getting the young ones onto the water.

Now if your looking at a boat for 12-16 yr olds they can rig their own boat so the unstayed rig is less important.

Its when the parents have to rig the kids boats the unstayed rig has the real advantage in getting boats onto the water.

This is where I started with the 12 ft concept and believe it is still the driver for such a design.

Regards,
Phill