Having looked at the images posted above I would prefer the Excelsior to be left alone, it has an iconic design, any changes to it would make it look like some bastardised sovvy/excel offsrping. It's the best Tac cruiser in the game bar none atm, it has a distinctive design and plays unlike other cruisers, I'm happy as it is.
I like the Excelsior ever since I saw it "Star Trek III: The Search for Spock". It is sleek and sexy with a mix of old school charm added in. That being said I look at the current situation of the Federation of having just been through a major war the spanned the Alpha and Beta quadrants. It is trying to move on from the legacy ships of the late 23rd and 24th centuries, but resources are tight. The Excelsior was the workhorse of the Federation for over a century; being constantly upgraded and refitted as need arose. It outlasted the iconic Constitution class as a frontline ship. It was popular with Admirals as their personal flag ships. It is cheaper to make and is a proven design. Galaxy and Sovereign class ships are expensive as is the Odyssey, and other large vessels. It is one of the reasons in the Expanded Universe that the Federation is turning to the Luna class as the backbone of the fleet (mind you this doesn't count in STO).
But, I don't believe that the Excelsior class needs a modern looking variant. I think it would just cheapen the old horse of the fleet.
I would like to see some other classes that have made cameos in TNG like the New Orleans class and Freedom class. It would also be cool if the did something along the lines of the Fringe TV series where parts of the Alternate Universe start bleeding over into the Prime Universe; where we could see Kelvin class, Armstrong class and Mayflower class ships showing up. The effects of Nero's incursion could be working their way up the timeline potentionally. I would hate to see them as lockbox ships though; I really hate that they put some of the neater ships in lockboxes. I understand the micro transations keep the game funded, but I think after a lockbox run ends those ships should go up on the C-Store.
Appearance would go to the Xindi Aquatic Cruiser. image
Sleek and sexy, and nice color scheme too. I think my only issue is the curvature of the wings, but other than that, she's a beautiful ship.
Performance goes to the Undine Nicor Cruiser. The ships in game are pitiful compared to the canon Nicors, even on elite. The canon Nicors were fast as hell, more maneuverable than a Jem'hadar Attack Ship, with more firepower than even the vaunted canon Borg Cubes. You want an example of what one of those can do? Watch "Scorpion" from the Voyager series. One Nicor destroys a half dozen cubes and disables just as many more. In following episodes you also get to watch a group of Undine ships destroy a Borg controlled system, and even a planet. And all the mighty Borg can do is run away.
Now if I had to do a combination of appearance and performance... that one is hard, but it would go to the Scimitar-Class Dreadnought. Simply put, she's a sexy lady, but don't let her looks fool you, she'll kill you in an instant with little to no effort.
If the main hull were a bit thicker in the vertical direction, I'd say this was the best Excelsior redesign I have seen. There are some real bad ones, notably the "slap Sovereign nacelles on it" examples.