As far as a sideways sliding turbolift on the bridge level, I don't believe the motion indicator ever show lateral movement when approaching or leaving the bridge. Unless it wasn't designed to do so.
We also saw, in the Enterprise Incident, about 20 vertical deck-lights go by on a trip from the bridge to deck TWO.
It's a TV show.
Yes, but that was Engineering Deck 2 in the dorsal.

The "pilot" Enterprise had the original Deck 2 under the Bridge, but the lowering of the Bridge for the regular series (VFX model) displaced what had been on this Deck 2 (WNM conference lounge?).
Since an accessible Main Deck 2 no longer existed, only Engineering Deck 2 remained, so when Spock said "Deck 2" the Computer understood he could only refer to E-Deck 2.
Also, according to my calculations / illustration in my TOS Enterprise WIP thread, the overall length would have to exceed the 1,080' figure to have a "centered" Bridge the way you suggest it, unless you lower the Bridge further to create the necessary space.
There is visual evidence that has not been mentioned yet, IIRC, from "Requiem for Methuselah".
Here we see the ship reduced in size with Terratin technology (

He probably knees down (not seen) but from within the ship that is the image we see: http://tos.trekcore.com/hd/albums/3x19hd/requiemformethuselahhd1157.jpg
Next, Kirk gets up.
Looks to me like the 30° offset is still a good compromise, as the footage would otherwise suggest it's even worse than we usually assume.

Bob