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
with Acad.