I want the framework to include a visual scene editor. I'm not going to go gung-ho trying to define features for it. I'd like to see it get developed in the same fashion as the framework itself: as a small, extensible core extended by community-developed features.

There are two approaches I can use to develop an editor. The first, more obvious one is to create one mostly from scratch. I can use the Mono.Addins component to provide the extensibility, and maybe Managed.Windows.Forms for the UI toolkit if it progresses quickly enough. I'd use the framework itself to handle rendering, picking, and so on.

Another idea is to use Python for .NET to plug the framework into Blender. Blender already provides most of the scene assembly features I need, all I would really need to add (I think) is the ability to associate behaviors with Blender nodes and assign their properties.

This isn't an either-or situation, maybe both get developed.