Well I think you guys are tackling this idea of a "bio-spaceship" wrong. First a good question may be to ask what qualifies as a spaceship. If it is just an exterior protectant that shrouds one during space travel then, I mean, by definition it is quite a spaceship. I feel the spirit of this bio-spaceship however is either "was it grown seperate from him for space travel" or "was it evolutionary designed as its main task to enable space travel." as far as it being grown separate from him that doesn't seem likely because his children are already wearing them and they are like less than 400 years old or something (presumable born after he landed at death mountain).
The second question seems very plausible to me because lavos is assumable able to take and integrate dna into his active dna. This being possible he may be able to just design any sort of form he would like for any sort of reason. However, his shell did seem to have many other functions such as his "destruction rains from the heavens attack" which he uses several a time just to destroy the world (12000 bc in the ocean palace and 1999). Anyways, I equate his shell to more that of like a turtle or so, it is used as a defensive barrier to thwart the environment. Which seems quite necessary as he goes from the vacuum of space and then to the center of the earth (assumable quite hot and quite pressurized). If I had to choose to label his shell with a form of biotechnology it would be a terra/spacesuit much less than a ship.
