Originally I planned to port blender, but its probably a lot of work for nothing. Lets stay realistic: even tho the blender homepage claims that it is "fast" - its actually not. It might be fast at what it does, but its not fast if its used the way it is by most people.
Blender has hundreds of features. Did you know it had a video editor? Did you know you can generate images using complex nodes? Animation using IK, multiple vertex weigths, a raytraced, hundereds of halo combinations, multiple shaders, a complete game engine, constraints and physics, ...
Its just by far too much.
Most people only use it for modelling and animating small scenes, add a node or two in the composer but then render using a raytraced, even tho it could be rendered faster than realtime using OpenGL with approximation and probably 99% of the raytracer image quality.
Let alone the fact that most exportable default formats in blender are not defined too well and they are in a text format. Personally I like my formats to be binary for easier loading, you are allowed to use bought models if the format is not open. Phyton kinda fixes this and its really powerful, but blender is not really realtime unless you stay really low-poly and in the 3D view, so Python is only good for really few things in my opinion as it can only simplify editing, but its restricted to editing and can't do much while your scene is rendered
I'm working on a blender clone so I can work on my projects. I'm not too sure which formats I make exportable, but it will support shape descriptions (for my 96k games), a object defintion list (for map projects, similar to GTAs IPL if you know that), probably wavefront for testing, a custom binary mesh and animation format. Thinks I care most about are: objects along curves, custom properties per {vertex, face, edge, ..}. Animations using skeletons are planned too even though thats not decided yet.
I plan to use the tool for ANYTHING in my games (except for animation maybe as I already have some sort of custom mo-cap system), including modeling, mapping, mission files (using custom properties per objects / empty, move of objects a long engine by adding a SCRIPT property). The tool is supposed to display anything, including the preview, using OpenGL ES2.0 with an ubershader for materials, shadowmaps for shadows, possibly SSAO which can be baked on the scene, reflectionmaps using fixed points and possibly custom shaders for full time quads as post-processing effect and shader editor.
If anyone wants to help with my tool they should contact me, but it doesn't have priority right now as blender works fine at the moment.