Hey pdb,
I'm also working on something with moving parts - I haven't seen any spec on movable parts for WSF or Aluminide, but I plan on shooting for a .2 mm clearance on the radius for my first test piece in aluminide.
As for the brittleness, it might be best to do a small test print and see what it can withstand - this is what I plan on doing for my smallest parts (3.8mm thickness).
Couple of points on your good looking model. Your "cross" mount is basically two unsupported wires - it might be stronger if you put webbing between them, like a swiss cheese I-beam, thicker where the cross meets...
Gussets on the sides wouldn't hurt - these don't have to be big.
I've got other thoughts, but you have a great concept there!
Will you be driving the gears with anything?