I'm planning to 3D print the white bits, so I'll spend some time improving their shape (and generally improving the awesomeness factor of this design). This shows the basic concept; everything is sized roughly right (although the span is a bit wide compared to the actual X4). Battery mount will be (somehow) integrated into the hub.

Don't worry, the eventual model will feature less beefiness on all the nylon bits. I don't want to add too much weight. Oh yeah, and the whole motor mount setscrew deal--you know, the whole reason for this project? I'll add that too.