Replacing Embedded blocks with another Block

I was asked if there was a way to replace an embedded (Nested) block inside of multiple blocks, with another block. I thought of Express Tool's  "Replace Block with Another Block", that that only works with blocks inside the drawing, not nested blocks. The only other way I know of is to redefine the block current block, then rename it to the new name.

Just to satisfy my curiosity, is there another way? 

Thanks.