"Should surely save weight, not needing a main set of undercarriage legs."
this is a concept, that was favoured by the good old Luigi Colani, too, who used it
in quite a number of designs. I don't know any more, where I read about it, but once
there was a report about the credibility of his designs, especially mentioning the concept
of the "symbiosis of fin and main gear", as he called it, too. And IIRC, the result was quite
disappointing : The fins of course would have to be beefed up considerably and in
most cases would have a shape, which would be less than ideal aerodynamically. And
the landing gear itself would be heavier, than necessary, because of the not ideal
load distribution.