I could do that... really, I could.
(Had to remap the saucer so that it'd accept a standard saucer-type texture anyways, so adding those two red lines will help with the look.)
But here's my take on things...
Let's say that the Excelsior project was a project that was a long time in development (like the original Connie). It could've started off as a testbed for new technologies in TOS times, and had multiple problems like underpowered nacelles (the technology not being in place yet for TMP and the higher powered TMP engines) structural reinforcement problems (a lot larger ship than even a Star Empire), and a good number of other problems that weren't resolved by the end of TOS. At this time, it'd have recieved and kept NX-2000.
However, with the refit of the Enterprise, new tech was available. A relook would've been done with the new tech available to refit and finally get the Excelsior flying and out of mothballs. The warp engines would've been totally rebuilt to provide more power for the huge ship, the hull totally rebuilt, and few systems would've been left. And then the transwarp engine project came up. Another hull reinforcement, and upgrading of the SIF generators to try and handle the stresses of transwarp. And then transwarp failure. Going back to the rebuilt non-transwarp engine design with all the new SIF changes and other transwarp reinforcements remaining in place. And there we go.
However.. mouahaha.. I have another idea that I'm trying to send to Azel in private for this design as well.. (grin).. However his Hotmail email addy appears to be not working, and all that... so methinks I need to send him a PM here on Taldren..