Until it gets written in stock...
You can write it into the POP0 menu...
;;; Average point of all selected points
(DEFUN c:average (/ |average| |count| |nextpoint| |pt1| |temp-pt|)
(SETQ |pt1| (GETPOINT "\nSpecify first point to Average: "))
(SETQ |count| '(1 1 1))
(SETQ |temp-pt| |pt1|)
"\nSpecify next point or RETURN to end: "
(SETQ |temp-pt| (MAPCAR '+ |nextpoint| |temp-pt|))
(SETQ |count| (MAPCAR '1+ |count|))
(STRCAT "\n" (ITOA (CAR |count|)) " points specified: ")
(SETQ |average| (MAPCAR '/ |temp-pt| |count|))
(command "_non" |average|)