IMO, the best way would be to use vlax-curve functions to return a point list which could then be
used to create a pline. The number of points would determine how accurate the trace of the object
was. If you wanted a more accurate trace you would need to determine the bulge of the curve and
create arc pline segments ILO straight segments. This would reduce the number of points needed &
produce a more accurate trace of the object.
My 2 cents.
PS I seem to remember Joe Burke doing something like this. Maybe not for ellipses though.