Maybe, it might also be easier to reuse portions of the engine in Unreal Engine while using parts of Unreal (like its rendering engine) than you think though. Assets largely I'd expect to be portable or at least comvertable with a custom asset loader.

I'm talking a little out of my ass though, and neither of us is familiar with the code. Point being though, it's a little different moving engines than rewriting a complicated web server (a project I have been a part of and would not recommend).