A few days late maybe, but if I could add my thoughts to the mix:
...Although I like the bigger scale for the Constitution class (mainly because it enhances the size difference between her and the NX class so it looks more like they made progress), at around 400 metres I think everything would be oversized. The windows would (I think, because I only did rough measurements) be around 1 metre high and the wider ones around 2 metres wide.
Furthermore, wouldn't the shuttlebay be too big for the shuttlebay sets (TOS and the films) we've seen? And I think the bridge (on the TOS ship) had to be shifted back to align the knob on the back of the dome (which I presume is the turboshaft) to the bridge set.
And of course there are the docking ports which would be way too big (aren't they oversized already?).
The size of the TMP Enterprise is of course fairly well tied down by the existence of the docking ports, regular window placement, the interior of the shuttlebay and so forth. It can be expanded a little but Bllsdwlf's 1164' seems close to the limit.
The TOS Enterprise on the other hand is under far less restrictions. The window levels are irregular, there are no ports or other scaled features on the hull and we see far less of the ship interacting with normal, human scaled objects (shuttlecrafts, workbees etc). The Flight Deck needs to fit in the aft section but we have no idea how long it is (the model was scaled to around 122' I think but we only ever saw it from one angle) or how if its height is the height of that part of the ship. The bridge turbolift is assumed to line up with the "nub" but this is never confirmed on the show. And a larger ship size would reduce the need to submerge the bridge into Deck 2. It might even allow the bridge ... to face forward!
I do think a larger TOS Enterprise works well. I also think we should consider the option that the TOS-E is actually LARGER than its TMP successor. The TMP-E would then be a sleeker, more modernised cruiser that has been stripped of its bulky outdated machinery; faster, lighter and stronger than before. Rather than welding extra bits on to expand the saucer's diameter and curve of the secondary hull, the change in shape is rather a result of parts of the hull having been removed. By reshaping what is already there, a lot more of the original Enterprise can remain intact as well (extensive redecorating not withstanding).
The interior sets seem to bear out this smaller size - the radius of the curved corridor is tighter and makes more efficient use of space with various compartments lining the walls throughout.
I appreciate that it flies in face of 25 years of doctrine, not to mention the designer's intent. However, does this theory seem viable?