I don't wish to appear I'm throwing Tab under the bus but the original question posed was "then which candidates seem deserving":
While other STOMs like Novak and Vivien Leigh appeared in a limited number of films they were major stars in their era. I just don't see Hunter being in the same "category".
So yea, Hunter has enough films to be STOM but I don't feel he is deserving. Someone like Edward Everett Horton is much more so and the overall film quality of a Horton tribute would be miles ahead of one for Hunter (IMO).
It's kind of like apples and oranges. Horton and Hunter were from different eras and the films they made reflect those different times. I'd like to see both get a month-long retrospective (separate months of course).
Since Tab is still living, and there is a recent book on him-- this kind of stuff ties in with TCM's on-air marketing. Also they could have Tab appear at one of their film festivals like they did with Novak.
When you look at how they design the evenings, they usually lead off with one or two well-known titles then the rest of the evening is the lesser stuff the stars did (the B films, the flops, the obscure foreign films, etc.). One night they can lead off with BATTLE CRY and go into his other war films. One night they can lead off with the two films he did alongside Natalie Wood and go into his lighter rom-coms. One night they can lead with GUNMAN'S WALK and go into his westerns. And on the other night they can lead off with RIDE THE WILD SURF and go into his low-budget fare from the 60s and 70s.