MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
This one almost fits the bill. It's not too hard to modify in blender, if you're handy with that. I have yet to try mounting this carriage (I'm still waiting for some brass bushings I ordered to arrive). When I get around to it and it's not a total disaster, I'll post it as a remix to this thing.