How about using a nested loop for hours and minutes in the REXX e.g.
DO H=9 TO 20
DO M=0 to 45 by 15
/* execute template here passing both H and M as parameters
END
END
In the template job have
JOB JOBESTFF.%H_%M
EARLYSUB %H:%M
I know that this is just an outline and not a complete solution, but its late here in UK and my brain is getting fuzzy