How long would it take to transform a human into a space-ship and back?
This is not a very hard-science-fiction tale, but more about human relations and adaptability, but I still want it to sound plausible.
A space faring civilisation that descend from humans uses bio-ships, but instead of engineering them from birth they are natural born humans trained in astrophysics that voluntarily choose to go through a mutation process in a special "bacta" tank/shipyard that enlarges their brains, giving them incredible memory and processing power, and alters their bone structure and body shape until they form the chasis of a hundreds meters long ship. They are then implanted and reinforced with armor, computers, sensors, reactors and such until they look like normal ships in and out, so they are both mutants and cyborgs.
These Bio-ships have the capacity of self healing and decision-making that a living being does, they value human life and do not have the alien logic and/or bloodlust an AI or captured space faring animal might have.
The ship performs its own duties of navigation, detection and weapon handling, but they are fitted with a crew for command, tactics, special sensor or weaponry use, engineering for the technology and care taking for the biology. Means of propulsion, survival in the vacuum, nutrition and oxygenation will be covered in the narrative but are irrelevant for the question at hand.
In the story, also, one of this ships crash and can no longer function, but instead of leaving her behind the crew has an emergency procedure (probably some genetically engineered handwavium substance in a big syringe) that can reform the original human body from the bloated brain-mass, like a cocoon.
How long should, semi realistically, take a 70kg human, grow into a biomass equivalent to 2 elephants?
And, years later, for its one ton brain to become a cocoon that spews forth a human?
Extra question: If the body no longer has a significant muscular structure or limbs to move, what size do the internal organs and the nutrient intake need to be in relation to the brain mass? 790