A long time ago I had a project called Gavit aiming to make prototyping, directed gameplay video and machinima authoring easier. The system was an extension of the engine’s infrastructure and assumed an intermediate knowledge of UnrealEd. The goal was to empower the user so they can show an idea without involving programmers.
After a few years I ran out of money and into some engine limitations so I moved on. The stuff was sitting on my HDD ever since and recently I was encouraged to release it so I did. You can find the download link on the project page: http://www.zoltane.com/pages/unreal/gavit/
Everything (code and assets) is licensed GNU GPL v3.0 and provided as-is, I’m not responsible for anything bad happening because of it. I will do my best to answer any questions you might have.
I hope someone will find something usable in there.