Let's get this over with.
Warning: This may be considered spoilers
I think preffered status players sholud be able to play some operations, not all of course.
Eternity Vault and Karagga's Palace. Do I really need to explain why? They are easy, they are quick, and they wolud serve as training or just warm-up.
Tobboro's Courtyard and Heart of Ruin. Some might not consider these "Operations", but they are inside a phase and that puts them as operations. Both are connected to Rise of the Hutt Cartel (Tobboro's Courtyard) and Ziost Storyline (Heart of Ruin). Both of these, like any other expansions, are playable by preffered status players.
Temple of Sacrifice. It's just plain cruel locking this for Prefs. As I said before, prefs can play all expansions... and they also have the "choice" to *SPOILER ALERT* choose between doing the operation or doing the dailies, near the end of Shadow of Revan. It pains to know you don't actually have a choice...
And I know that by this logic, Gods from the Machine sholud be unlocked too, but Gods from the Machine is the big work in progress and it's understandable why lock it for prefs.
Out of 12 operations, including Heart of Ruin, Tobboro's Courtyard, The Rakghoul Nightmare, and Unity Assesment, wolud unlocking 5 be too much? No. Oh wait, BioWare's greedy aren't they...