Here's what the designer, Ian Richards, has to say about the process of creating this new design:
When I was tasked with the creation of the refit version of the Sovereign, I knew I had to draw from other 2409 ships seen in STO. The standards were set pretty high, seeing the Venture class refit of the Galaxy, the Thunderchild and Armitage refit of the Akira, among others. All of these ships had something in common, namely, selling the idea that they are an advanced version of their original counterpart, while keeping true to the basic design features. The Sovereign is already a gorgeous ship, so I knew it would not be an easy task to make it even cooler.
I took design features seen in an assortment of ships, from the Defiant, to the Odyssey, and everything in-between. Most importantly, I had to make sure it paid its dues to the Sovereign, so it kept the overall shape and size. A few key features were changed to help make it stand out, namely the forward swept pylons, and the grand arms stretching across the ship, from the front of the saucer to the rear shuttle bay. The top of the hull was ideal ground to do something to help it stand out. It's a mixture of what is seen on the Sol, Venture, and Sovereign. Creating negative space from different perspectives was massively important to making the Regent what it is today. From the side, there is no negative space between the Nacelles and the hull of the ship, akin to the Venture class. The inward facing windows on the rear of the semi-split hull is akin to the Odyssey and Sol. Some of the details under the saucer are not only directly inspired from the Constitution, but also from the Defiant and Intrepid.
In the end, keeping familiar elements from other ships, and merging them together into one glorious vessel, results in the Regent. While the Sovereign will always have a special place in my heart, I'm very happy with the end result of the Regent. I feel that it will perform quite well as Starfleet's primary assault cruiser.