If it turns out that Mini-fillia is the one place where they ditch the "it's been 12k years since the Shards split from the Source so there's no good reason for there to be alternate versions of other characters on other Shards" idea, I will be very disappointed.

Alternate versions of major characters in this setting make no sense. If the writers have to stoop to giving another shard a version of Minfillia to have Source!Minfilia be involved with the plot again, I will think they are very lazy writers indeed. And this is in an expansion that has been dripping with contrivances since it was introduced. The last thing this expansion needs is just another "it just so happens that x happened".

I would much rather have Mini-fillia not be anyone from the 1st Shard. Having her come about due to Source!Minfillia messing around with the 1st Shard and letting her human side be born again or something makes far more sense.

If there was one thing Stormblood taught me about the FFXIV story team, it's that their lore is usually well thought out (so long as Youshida isn't to heavily involved; see Eureka for that). However, their implementation of how the lore is shown to the player through the story has been very lackluster. In particular, Stormblood had a badly paced Expansion MSQ (4.0) and Transition MSQ (4.5). Having to contrive circumstances that Minfillia is involved in the 5.0 MSQ just makes it feel like we are headed into more badly paced MSQ again.