Try this on a dwg
(vlax-for ts (vla-get-textstyles (vla-get-activedocument (vlax-get-acad-object)))
(if (= (vla-get-FontFile ts ) "Txt.shx")
(vla-put-FontFile ts "Simplex.shx")
)
)
Using a script can run this very simple lisp program, for 500 dwgs accoreconsole is the way to go you have a script that loads the lisp.