Thanks, that actually works.
I think it will work for all the blocks except as expected, for the Dimension block.
With the Dimension block, the arrow, offset, etc. are no scaled for some reason. If it's done manually, it's adjusted from the Properties toolbar by changing "Dim scale overall".
(defun BlockInsertAndScale (blkname)
(command "_.-insert" (substr (strcat blkname "-" (menucmd "m=$(edtime,0,yymoddhhmmss)") "=" blkname) (+ (vl-string-position (ascii "_") blkname 1) 2)) pause (progn (initget 3) (getreal "\nEnter scale : ")) "" 0)
(command "explode" "last")
)