The TARDIS interior has been analogous in size to a small moon, or least has the potential to be that big on the inside, the Doctor's I think has shrunk over the years, he's jettisoned a lot of modules over time, but still, think BIGGER IMO. I'd put it more in line with the size of the Deathstar.
I can accept that it would have the potential to get that big.. I want to do a large schematic at some point showing a Tardis over grown, so much so that the outer lengths have become blackened and decayed because it grew too much.. kind alike a cancerous Tardis.. it just wouldn't stop growing.. and to do so it lost the ability to traverse time, and just sat there gorging itself on the particles and energy it drew from the rift via it's time sceptre..
IMHO the Tardis should have an optimum size.. and if it got too big, it would then have to release those sections or face serious problems..like the overgrown version I have described.. to make a Tardis as large as you say it should be, would cost tremendous energy to maintain.. and to do that would limit it's potential.. consider that also in the novels that the Tardis is shrunken to about the size of a small space ship as it was not needing the extra rooms for exploration..and was used for war.. so to conserve energy the war Tardis was made intentionally smaller..
and even still were the Sentient Tardis, which were even smaller then the War Tardises.. so honestly..while the Tardis I have designed can certainly add on multiple sections and more pillars/columns to hold back the dimensional forces..I would think that there is an optimum range which the images I have given depict.. I mean rationally what would the Time Lords need with more then a ship which is 2,550 feet long? with all those rooms and sections.. what else could they possibly want to include in the Tardis? The ships were supposed to be designed for exploration, and yet they never used them for more then that...
why build ships the size of Deathstars, and yet not use them?
why would the Tardis be the size of a deathstar to begin with? I think that our perception of what we think the tardis is in size is because the series has never quantified the size.. so left un-realized.. we tend to think it is bigger then it is...
I think it has the potential to get the size of a deathstar.. but realistically i think that 2,550 feet in length is quite large enough, and realistically is believable considering the particles and energy needed to sustain itself in its own dimension, and still be able to traverse time and space..
But I love this idea of a Type 40 Tardis that has overgrown itself so much so that it has become a decaying and monstrous machine..
a ZOMBIE Tardis!
I love it!
Brent, in a round about way, you just gave me a Great Idea! thanks man!