I'd beef up the fragile neck and nacelle pylons, and make the whole thing bigger. Thank you, Ryan Church and J.J. Abrams!
The Enteprise doesn't just go out on six moth cruises, people live aboard for good chunks of their lives, so I would make the interior more "home like." Not necessarily the bridge or engineering, but the corridors and the living quarters, and especially the rec room. Delete the Costco Wholesale cargo hold. Outside, change the color of the silver hull to a semi-gloss white.