I had no idea so many FFXIV players were vegan! Usually this level of judgment isn't something I see outside of vegan communities, so it's interesting to see its prevalence within the FFXIV fandom.

Re: Zodiark

Well, we don't know what life he created, it's all speculation. We do know that the Ancients couldn't create souls, so it'd be reasonable to conclude that neither could Zodiark. Also, aether is aether, I'm not sure it matters where it's sourced.

I found a translation from Japanese of Hythlodaeus' dialog in ShB. It doesn't differ much from the English, but it says: "The earth was dead, the water polluted, and the very wind still. Thus did a further half of the remaining people offer up their lives to Zodiark, that he might cleanse the planet and seed new life on it." This implies that 1) there wasn't enough left living or uncorrupted on the planet to use for aether other than the Ancients themselves and 2) that the 'seeded' new life wasn't fully formed to have enough to aether to use, hence the plan to wait until it had 'flourished'.

Given that context, sacrificing a bunch of saplings wouldn't have been enough aether. Trees that had grown into great oaks would've yielded much more. Also, I don't think people are using "sapient" correctly. None of the new life would've existed long enough to have developed sapience. I think you mean sentient. Regardless, this also brings the timeline into question. Granted, I can only apply real world growth cycles, but even if we assume they were going to sacrifice sentient creatures most of those would've needed about a year to fully develop. I'm speaking specifically of animals here, to be clear. Any humanoids would've required much longer.

Additionally, Elidibus had exited Zodiark to help mediate the conflict within their society and surely they would not have engaged in a third sacrifice while Zodiark lacked his heart, if they had even reached that point since it sounds like it was still under some measure of debate. So, if we assume that Venat had always planned to sunder the star, then there are some significant time gaps and circumstances that don't make sense. You can't say it was to get organized either, the Anyder dialog indicates they had been stalling. I'm left to conclude that Venat actually did believe the Ancients capable of handling Meteion, but perhaps because not enough of them joined her side as quickly as she wanted she decided to take matters into her own hands. It still blows a hole through the dynamis defense since if their only salvation was ever going to be the sundering, then there would've been no reason for her to bother with outreach to her people or to put it off past Zodiark restoring the world.