There was one done along those lines several years ago, mostly from parts of the Polar Lights kit. You can find it (and the massive station it's attached to) at the bottom of this page.With the passing of Ralph McQuarrie and the release of the M. Falcon book--I wonder if it might be a good idea to make a Federation saucer based on the Falcon (minus the cockpit escape pods, etc) with the very simple details for a Planet of the Titans ship saucer...
Here's some direct links to pics of the ship itself:
1 2 3 4 5
Using the Falcon as the saucer was also done in Zapped!

linky