After export as 2007 ASCII DXF, I can see the sketches in each layer. As you mentioned already solid cannot be display, I have to export all solid in BricsCAD as SAT and import in MoI, then reassign each to MoI Styles (layer).

But I encounter another problem in Boolean Diff, the surface of the resulting block lost some face if I choose to keep the subtract object. I will email the 3dm file to you.

the free 123D Design 2.2.14 opens directly DWG and accessorily resolve complex fillets for moi! ;)

(import/export: DWG, Sat/Step) so cool for moi!