The only CAD that I know of that implimented
characters with special "block" was GenericCAD.
Icad and Acad use compiled shape definitions
(SHX) files which can't be exploded directly.
I had placed the GenericCAD-style font support
on a wish list a long time ago. That implimentation
allowed fillable fonts as well as SHX-style
and you could create new fonts by simply drawing
them...Much better than the ACAD system.
This is one area where Icad could part ways
Go here and see if it helps you: http://www.cadopia.com/ubb/Forum5/HTML/000208.html