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.
Fireprinto, you could split the inner core in two pieces and print seperatly, bridging should work since the inner is square.
The outer not a clue.
Just some observations from the picture of what you trying to create: