Solution 9 - Unfounded Speculation!

[Iscah]

Emet Selch says at the end of Endwalker: "Some of che civilizazion in the reflections will surprise you"

So I think Solution 9 comes from another reflection. The other worlds have not had calamities, so it is likely that their civilization has advanced to a very high technological level.
The problem is how it arrive to the source

The "problem" is that people keep drawing this flimsiest of connections to a line that is probably just paving the way for us to actually visit other reflections (plural) in the future. It also assumes that we're going to burn through all of Emet's sightseeing recommendations in a single expansion and leave nothing for later.

Additionally, after Y'shtola has put so much work into devising a way to cross the rift, it seems unfair to just drop the answer in her lap from a civilisation that already has it figured out.

[Vyrerus]

The "problem" is that people keep drawing this flimsiest of connections to a line that is probably just paving the way for us to actually visit other reflections (plural) in the future. It also assumes that we're going to burn through all of Emet's sightseeing recommendations in a single expansion and leave nothing for later.

Additionally, after Y'shtola has put so much work into devising a way to cross the rift, it seems unfair to just drop the answer in her lap from a civilisation that already has it figured out.

I mean... that's kind of what always happens though. The dropping of solutions into her lap. See 6.55 with Cid's offscreen innovation to make the whole funnel Light from The First to the Thirteenth, and Y'shtola just showing up with the device as if it were no big deal.

See again the solution for Tempering.

See again the antidote for the poison back in SHB.

See again The House of the Crooked Coin for Seiryu's Wall.

I'm sure if Solution 9 has her answer, we'll have to fight a dungeon for it or whatever, but I kind of doubt she's gonna innovate a portal on her own. That is what would be uncharacteristic of XIV and Y'shtola related situations.