, you are definitely onto something as regards cargo/supplies stowage and transfer (although the actual designers of these photographic models probably didn't spare any thought to such things). With the increased reach of a successful transwarp drive, there would have to be a logistics revolution in Starfleet - and the Excelsior
, no matter how experimental, was certainly built with success in mind, featuring all the familiar elements of a deep space exploration and combat starship as defined in TOS and redefined in TMP. Plus more...
The "more" could certainly be logistics-related. Or then it could be a side effect of the ship shunting all of its truly
experimental and untrustworthy bits into the lower keel area, and keeping a path clear for dumping them to space at the earliest sign of trouble!
(And, I concluded transwarp to be a failure by the fact that they didn't call it transwarp on TNG, and later by the fact that other races had something called transwarp.)
But taken literally, transwarp is "beyond warp", "the next thing after warp". Once adopted to use, it ceases to be transwarp, and the sights are set for the next
Which is why all sorts of completely unrelated FTL drives can be "transwarp" at the same time, or at various points of history.