Here is an answer to the size factor.. this is what the Tardis would look like when it is grown to a Maximum
Now I am going to work up a Zombie Tardis.. I love the idea..that a Tardis would corrupt itself by overgrowing, and then start to decay and eat at itself, and then become a zombie of sorts.. seeking out life to sustain itself, thus corrupting that life and turning those beings into zombies themselves.. until they turn to dust.. and the Zombie Tardis would make an excellent plot for a show..
I can't wait to start work on that..
anyhow.. a Tardis will grow and then stop, unless something is wrong and then it gluts on th energy it thrives off of from the universe, and the engines phase, and the ship starts to feed on itself and... well you will see..
I need to finish the basics of the type 70, coming soon..