what about modemacro?
I have a nearly identical command that does not use lisp and puts the dimscale as modemacro display.
main difference is it is a set dimscale command, you enter the ratio (i.e. "16" for 3/4"=1'-0") and it updates dimscale and displays the scale you just set until you reset it.
Only hitch is you don't display scale when a drawing is first opened until you hit this button.
^C^C_dimscale;\_MODEMACRO;DIMSCALE=$M=$(RTOS,$(/,12,$(GETVAR,DIMSCALE)))"""=12"""_;