Have you tried performing Global Attribute Editing?
Invoke the ATTEDIT
Command to edit multiple Blocks' Attributes.
Otherwise, you will need to perform something really time consuming via creations of "Unit Blocks" in new directories & with new names.
This would involve opening individual Blocks, editing the Attributes individually via the DDATTE
Command, then "Write Blocking" them under new names in a new directory via the WBLOCK
I am very sure there's a simple global or multiline text/attribute edit function in the >2000 versions (anything above R14), since these versions allow multiple items to be open in the same session - whereas my R14 version is extremely "DOS-Like" in nature, and only allows one drawing open per session.
Will check around with the "More Modern Users"
to see what they say.