I really hope they don't skip over doing a Stormblood (SB) MSQ Ultimate, I think there's plenty of really interesting ideas they could use from the expansion's themes to make a compelling and fun fight. In my opinion, completely skipping over it would be a missed opportunity.
Manny of my thoughts have been centered on the raid being in an alternate timeline, somewhat like DSR. This would focus more on a what if scenario, being: "What if we redeemed Fordola and Tsuyu before fighting Zenos?" I believe that the backbone of this fight would center around three Zenos fights, with the last of course being the final phase of the fight, and the unique form we always see in these raids. The first two could be scripted losses in a sense, having certain DPS checks in which you survive by the skin of your teeth. Say, the first one is akin to your fight with him at Rhalgr's Reach, where he mops the floor with you. Get him past 75% health, and he does his signature knockback move and gives the party Down for the Count, allowing for a phase transition.
Then the second phase kicks in, being Fordola. This would likely be the toughest ask, seeing as it would likely require them to make another unique model for her. I think it would be an interesting take to have this be some representation of a historic or religious figure of Ala Mhigo. Perhaps this could have elements of Rhalgr, along with the perversion of Garlean influence. This is where you would see the sort of puzzle mechanic, maybe having some form of "sparing" her, or a mechanic to get her on your side? Something like that.
Then of course, we would transition to the second Zenos fight. This could be Shinryu, with him now seeing you as more of a threat with Fordola (and Ala Mhigo, in a thematic sense) backing you. This would be another scripted loss, though you would certainly pose more of a threat to him this time around, with far more health being stripped from him than previously. The next phase would be easier to implement, being Tsukuyomi. Similar to Fordola, there would be a sort of redemption or sparing puzzle mechanic here, which would then lead to the final phase.
Think about it, an alternate timeline where you were able to save Fordola and Yotsuyu both, a story of redemption before we encounter Zenos for the final time. I believe that could make for a really fascinating fight, with their assistance empowering us for that last push. And with an orchestral theme of the Stormblood leitmotif... I at the very least would be thrilled to do this week one.
I don't claim to be a master, or even half-knowledgeable about fight design. I'm sure this idea poses many challenges, or may not be manageable. I more so wanted to point out that there is a multitude of ways they could take a SB story Ultimate, so I really, really hope that their plan isn't to just skip this and go straight to Eden and Shadowbringers. There's my rambling!