I think plywood planking is actually easier for a beginner / novice builder.
Framing structure should largely remain the same either way.
Caulking seams between solid planking is as much an art as a learned skill , something
which may be foreign to even the more experienced modern boatbuilder.
I have read numerous discussions on caulking methods and even use of materials , and was quite surprised to find that even the “experts” do not entirely agree on what to use , or the method.
Best left to someone who has successfully done it before.( Personally I have not done this , and at the very least , I would want to be shown or taught by someone who has.)

You are absolutely right about the choice of material for the windows.
It has to be wood only , nothing else could look , or feel as “right”.
As for doors , again , wood is the choice .

As to size , I agree there also. Maybe a little larger all `round.

I like this boat.

While the GT 27 is a nice appealing boat , there would be considerable savings both in time and money to build a plywood pontoon boat .

If you really want a house boat , consider building a pontoon boat of plywood , that offers the same ( or likely ) more space and accommodation that the GT 27 does.

http://www.pontoonplans.net/wp-content/uploads/2010/07/Pontest4-1024×484.jpg

http://pontoonplans.net/wp-content/uploads/2010/07/AA.jpg

Mike