very interesting.

I do think you are right in thinking that the 'defective cottage' was a tongue in cheek comment by JA to describe Barton cottage.

But I have to say, I do like the 'non defective' ones very very much :)

I don't know if JA was being satirical about the picturesque, because the passage describing the position of Barton cottage seems real enough.
Maybe she made a distinction between 'man-made' pictureque things, and 'natural' ones (unless I am mistaken, and cottages didn't really come under the 'pictureque').