Yes it is. I'm really regretting coining the term DTD at this point when it seems there were so many other, better terms available!
If I can accept the dramatic change from the S1 Engine Room to the S2 rebuild, then why not? And this all makes all kinds of sense in terms of a (somewhat rapid) technological progression.
The only downside is that it would negate the need entirely for a second Engine Room (of the same design, anyway) and due to the presence of the curved corridor it would place Engineering headquarters squarely in the saucer.
This matches up nicely with TMOST and Franz Joseph's plans, but conflicts with DOTD (unless the pinwheel alien took a tour first).
Perhaps there was always a TMP style Engine Room in the TOS secondary hull, only in TOS it was a hazard-suit only area? As a result of the refit upgrades, Engineering HQ was moved to the secondary hull?