You are basically proposing changing everything that defines what makes an Unreal Tournament game.
The weapons, more than most other aspects, define the game. Changing them, changes the game. You're talking about a total conversion mod, or a new game to be developed on this engine.
Some of the more or less unique aspects of UT that attract it's player base are things like extreme variety in the guns, and what and how they fire, the dodge, the translocator, the lack of reloading or clips, the fact that it's not class based, the fast pace, and the the fact that it is an arena shooter.
There is also an underlying depth to the gameplay from all that stuff, that most people don't grasp until they get to a competitive level at the game. The tactical side that JD spoke of.
It's not just because it's an arena shooter with pretty graphics that people play it. Hence changing that other stuff will kill off most of the current player base.
My suggestion: Go play these games you sight as examples.
My question: What is it about UT3 or Unreal tournament in general that makes you want to bring that style of play to this title?