I don't think FF needs to be turn based, and if they want to keep going action for cinematic gameplay experience that's fine. Just need to do like 20x better than XV and XVI at having RPG aspects to the combat and skills and choice. If they CAN'T do that in an action gameplay, then sure lets go back to a turn-based framework.

I had an idea in my head after playing Unicorn Overlord of an FF game with "programmable" encounters, but you can switch your party through different jobs like FFXIII Paradigm Shifts, and I feel like that has potential.

But what XVII actually needs to succeed has very little to do with it's gameplay. What it needs to succeed is colorful party members (not all one-note wearing black like the XV boy band), a full party (not Clive and random tag-alongs like XVI), and a charming engaging antagonist (lets go back to the FF greats like Kefka, Sephiroth, Kuja, hell even Emet Selch for recency). The characters will carry the marketing and sales. Get a good cast and throw them into a fantasy adventure against a compelling villain, and people will play it. XV and XVI both fucking sucked in these aspects. XIII had half of a good party, but also failed in the other parts.