Why Erenville succeeded as a character where others did not

[Cleretic]

MY question would be, whats the difference? why does Eternal memory use up souls, while those constructs seemed to be fine until their creator died and their power was used up?

Permit me an 'Um Actually' here, but the Endless don't consume souls, they consume life force, which is a different thing (and was stated more clearly in Japanese but they are at least consistent about what terms are used where). That's a thing that can only come from living people, so it's not much of a difference, but it does mean that the Endless aren't powered by souls, that's not part of their system; the souls go to the regulators.

But yeah, you're right: Anabaseios Erich and Lahabrea are pretty much exactly as 'fake' as Living Memory Namikka and Otis. And yet we never threw stones at Anabaseios' story for that, and the story itself treated both instances exactly the same: as people, not as some frankensteined non-person. If we trust the story to be right about itself, and to be teaching us the right way to read it, then we should take it as the story does: that they're people, deserving of all the respect and dignities of people, regardless of whatever intangible element they do or don't have.

The far simpler solution would be to give all of the Shetona that standard Viera accent, just like Lyna has it despite being raised in a culture with a predominantly different accent. Erenville, even if not originally planned to be Shetona, is still the first Shetona character in the game and so should be a reference point for what follows.

There are a number of locations specified as being in "the Shetona language" so it's not a stretch for them to have a different accent to the other cultures if they're intended to have a different language. Accents in FFXIV have been race-based for such a long time that it's bizarre they've chosen this moment to decide that everyone from the same location gets the same accent even if it messes with an existing character fitting into his own culture.

Or at minimum, give Cahciua that accent and imply that she's Othardian Viera originally.

And see, that would just leave us with a different question of 'why is every viera Icelandic, even the Turalian ones'. Even I'd find that a harder buy than 'Erenville's adopted an accent for long enough to not drop it around his mom'.