Mostly Not Masters and Not great stories.
I just finished watching the entire 6 episodes. As someone who has read Sci-Fi stories steadily for forty years, I would classify Heinlein as a master of the genre. Both Sheckley and Ellison are excellent writers. Sheckley is considered one of the best short story writers in the genre by many other writers, including Ellison. From '67 to '80 Ellison put out 8 excellent collections of short stories. His story "Jeffty is Five" is one of the greatest short stories ever written, but with no action or special effects it wouldn't go over very big on TV.
Of the other 3 writers Howard Fast was a great mainstream and historical novelist, not really known as a Sci-Fi writer. Same with Walter Mosley, a crime novelist who has dabbled in Sci-Fi. Kessel is at least a prolific short story Sci-Fi writer. Winner of the Tiptree Award, but not IMO a master (yet).
I would have picked some stories from the late 40s to early 60s. Anything that wouldn't necessarily be dated. Some stories that have always stuck with me:
"Rule Golden" by Damon Knight (one weird alien and lots of action)
"Huddling Place" by Clifford Simak (one of many great short stories comprising
his novel "City"
"Or All The Seas With Oysters" by Avram Davidson (really makes you think)
"Mimsy Were the Borogoves" by Lewis Padgett (a pseudonym of Henry Kuttner and
C. L. Moore)(a story on the same theme as "The Little Black
Bag" by Cyril M. Kornbluth)
"Scanners Live In Vain" by Cordwainer Smith (a pen-name of Paul Linebarger,
far-east advisor to JFK)
"The Weapon Shop" by A. E. Van Vogt (very topical in today's political
environment)
"The Nine Billion Names of God" by Arthur C. Clarke
These are just some of the thousands of good old Sci-Fi short stories that could be easily adapted to half hour to hour long teleplays
It's only with the heart that one can see clearly. What's essential is invisible to the eye.