Random thought regarding this design: I noticed you were using punched and folded sheet metal for your chassis. Have you thought at all about using the same for your module? The precision is doable, and should be cheaper than a pure milled construction. You also might be able to find a middle ground with some parts milled and some punched to cut down on cost.

For example, the top plate of the module milled, with punched sheet pieces for the "yokes" of the module.

Might be something to take a look at for cost reasons.