There's actually not as many scenes set inside turbolifts as you might think - but in the case of Marvick's Ride (TM) I think the sole use of up/down bars is justified, as your turboshaft doesn't really go anywhere else - the horizontal motion is only for a few metres until it connects with the main diagonal pathway, why would the turbolift bother with left/right bars at all?
Since the Marvick turbo lift in an upgraded illustration of Deck 5 would have to move horizontally the same distance as Spock's turbo lift in "Amok Time" I see your point. But if I remember correctly, we didn't see the last meters of turbo lift travel in "Amok Time".
An alternate approach would be to have "Uhura's turbo lift" at the 9 o'clock position in the deck plan (it could just "drop down" into the diagonal turbo shaft) and have the Marvick turbo lift drop down at the 6 o'clock position onto Deck 6 where it continues to travel horizontally. The TB footage would just have to allow for sufficient "drop space" down to Deck 6...
Which reminds me to get back to our problem of the rather short turbo lift ride to the Bridge in WNM. I just noticed that the WNM transporter room corridor I had featured in the engineering hull deck plans would be an almost perfect mirror image of the 10 o'clock corridor with the angled in "hangar deck door".
We'll see that on Deck 6 and apparently the transporter room from WNM and "Day of the Dove" could be one and the same...
Yes, the empty spaces will allow us to put things there we haven't seen onscreen. TAS material will definitely be considered (Deck 7 will be a good start with the starboard impulse engine room), though I believe the zoology lab would be a facility better suited for the engineering hull.
Great feedback and inspiration, keep it coming. I definitely do not see all the options available.