These two types are useful in their own ways, and derive from different
classes. If DrawingBrush types are the only option now, then that requires a
lot of very tedious work to convert them to DrawingImages.
Design1 exports objects in a very clean way that allows you to rename them
later, the default is to name each object UnnamedObjectxx where xx is a
number. That is easy to deal with. Design3 puts everything on one page to
let you struggle with it later.
If in fact exporting to DrawingBrush types is the only option now, would
the Design Team kindly consider adding DrawingImages back again in Export?
Sean