Composites allow fancier, swoopier outer mold lines for not much difference in production cost.
Composites have the advantage of limiting corrosion when scooping water from the ocean. Corrosion is always a problem with seaplanes.
The longer single tail makes way more sense than the triple tail on the short aft fuselage of Canadairs.
Finally, mounting the main wheels on sponsons frees up critical fuselage volume near the center-of-gravity. That space is better filled with water. Hopefully they can elminate those annoying fiberglass water tanks - that extend above the floor on Canadairs. A straight, flat cargo floor will simplify loading sand-bags, hoses, crews, evacuees, etc.
If they make the cabin cross-section large enough for LD3 baggage containers, they can haul over-night freight during the rainy season. Notice how Fedex commissioned Cessna to build the 408 Sky Courier and tailor its cargo compartment to accommodate a triple set of LD3 containers.
To that end, make the aft cargo door sill flat and extend the sponson aft so that it can act as a loading ramp when pulled up to a dock. If you still want to load via fork-lift on asphalt, then install a second cargo door on the opposite side, and farther aft, behind the sponson. In a perfect world, airplane cargo floors are the same height as truck beds.
Similarly, making the cabin ceiling more than 6 feet tall (2 meters) will allow passengers to stand on their hind legs like gentlemen. The firefighting interior only needs fold-down cloth seats ala. C-130, but tourist versions could get fancier interiors. Mind you, when I am playing tourist on a short sight-seeing trip, I care first about large windows and seat configuration is last priority.
