What exactly do you mean by "Complex Hatches"? You can create new 'materials' for RAC utilizing ACAD Hatches, both Model and drafting types, and yes they would come from the acad.pat file, which is text based.
Virtual World Designs
VDC & BIM Model Design, Clash & Coordination
Building Design Suite Ultimate 2013
Charlotte/Gastonia, NC & Jacksonville, Fl.
You might also try this:
Registered Architect/BIM Manager
Thalden Boyd Emery Architects
St. Louis, MO