I love a good technical manual.
What do you think of the Tardis being a tessaract wihin a texture, a 3D cosmological defect like a cosmic string?
If nothing else, to have the Doctor exclaim "Defect!?"
Warning, a rather lengthy reply to follow... TARDIS LEVELS: Think of the TARDIS that looks like a molecule model, or Atom. It's rings with Domes all circling around the central engine, and eye of harmony. As with the Prometheus planetary map concept from the movie, whereby the 3D graphic shows orbital paths, and planets rotating. In the TARDIS, these paths would represent the corridors, which can move and spin to connect with different sections around an orbit relative to the main section. each room is either connected to the corridor, or separately floating in this limbo until needed. The TARDIS can create more rooms, and attach them to the corridors at will, or delete a room, converting the matter (a flux state of matter) into energy and feed it directly back into the main engines. These rings and rooms each represent a specific floor. as the TARDIS grows in scale, new rings are formed spiraling out to the next floor and rings surrounding the previous floor and rings, and central engines. Think of the TARDIS to use the analogy coined by Shrek the cartoon character.. The TARDIS is like an onion. It's many spherical layers swirling downward and outward to form it's interior. The difference between a Tesseract, and a separate Bubble dimension is that in a Tesseract you have one space, which is being supplanted by another space as you move within it. It's like being in the Holodeck on the enterprise. It's an illusion that you are moving in a larger space, but in reality you are still in the single room. In the Tesseract, you are in the same spot relative to space, however your room is being supplanted by another as you stroll in. In the Case of the TARDIS, and according to Dr. Michio Kaku as noted in the Doctor who 7th series special, the Technology of Doctor Who, Dr. Kaku explains how the TARDIS is clearly a separate bubble universe off and yet still connected to our universe. This data falls in line with the Eye of Harmony, and the episode where the Doctor goes to a bubble Universe that is slowly collapsing to save an alien there which moves extremely fast, and is grotesquely humanoid. The Doctor explains that such a reality will collapse because it does not have an infinite source of power to sustain it. Which is exactly what the TARDIS has. In this manner you can extrapolate that a bubble universe would not have a set up-or down, nor would it have it's own gravity, or laws of physics except that upon which it's whole existence is determined by the set of mathematical principles set out in it's initial formation. Since it is made from our universe, certain principles will apply, however since it is cut off from our linear time, the principles that govern time in that Bubble of Quantum Foam, would need direction, hence the Time Column, and allocation of time which expands space within the bubble and allows multiple forms of existence within, on a 3D scale, and multiple rooms out of time and sync with other sections. Anyhow, back to the Levels description. As the corridors spiral out to different rooms, and some are static, remaining in place, some are orbiting and moving according to the Psychic needs of the pilot and crew. In some cases the ship's corridors can manifest additional pathways as short cuts to other sections, or gravity well lifts to other corridors, or some domes are actually junction nexuses which have places where corridors and rooms can intersect in one place, and then lead out to other sections. As you move higher in the spherical layers you ascend to another floor or level of the ship. As you descend in these spherical layers you get closer to the center of the TARDIS, where as noted by the Doctor in the episode Big Bang, River song was in the center of the spherical exploding TARDIS held suspended in Time. this would denote that the Main Console room is close to the Main engine section, and would fit with my assertion that the default bulk of the ship is in the middle of a spherical format. The eye of Harmony is off the central engines, and as you get closer to the middle of the ship, the Dimensional pressures become more pronounced, and give one the state of euphoric impressions, and such. Form the most part, the TARDIS rooms, and pool and such exist in the outer main rings or main floor, where the sections closest to the Main engine and Power Room, are connected to the "Bowels" of the TARDIS and considered the lower floors or decks as an inner set of rings. each room has it's own gravity orientated to the ship's direction. Each dome as it is , can adjust internally to the motions of the rings, and orbits around the central section. An example of this would be a spherical compass set in water. as you twist the outer clear ball, the inside remains level because of the pull of the Earth's gravity. as these domes orbit and connect to their corridors and such they too can adjust internally as it's outer validium shell moves to connect to it's respective corridor when needed. These connections become firm, once a layout is chosen after restructuring the ship's interior. However other Domes can be detached and ejected when not needed. some domes and corridor connections to these are dimensional link junctions, which connect that junction to another dome junction which can take you instantly from one section of the ship, to one of the higher levels, instantly arriving at another part of the ship, where normally it would take you days or weeks to get to. These junctions are few in nature because too many would destabilize the interior dimension. imagine if real space was plagued with nothing but mini wormholes all over the place, that would have a detrimental effect on our solar system, and universe. in the Type 4o Tardis these junctions are present only a few areas, but are inactive until needed by the pilot or crew, this is to cut down on Dimensional instability.