The problem here is that we have no real idea whether he is even aware of other "solutions" existing. The Ascians act on the knowledge they have, and whilst it is considerable, they're apparently not acting under Zodiark's active guidance, or else the XIIIth would not have succumbed to a flood of Darkness. Now, if the Ascians believe that all creation stemming from the fragmentation of the worlds is false - as Solus suggests - then they may be rather uncompromising in their desire to hit the "reset" button, and we do know that some amongst their ranks revel in causing mischief, i.e. take pleasure in the means as much as the end goal. At the same time, there are probably those who act out of a sense of duty to Zodiark, and possibly some who have grown fed up of it. My guess is that Elidibus falls into the former category, and Solus into the latter (especially if he is possessing Varis, unbeknownst to us all), whereas Nabriales and Lahabrea, and perhaps some others, find greater enjoyment in the means than the end itself.
As for the Rejoinings not being viable, well they certainly are "viable". They may not be desirable to those who would be sacrificed, certainly, but they're viable all the same as they will achieve the desired end result.
Then there's the question of the fragmentation of the Source and the Reflections being an inherent source of instability, if the breadcrumbs Banri Oda gave at the JP fanfest are to be believed. If it is the case that the Crystals must be rejoined, Hydaelyn's opposition to Zodiark and intransigence towards it would be motivated by a benefit to her, namely not being rejoined to him. I'm not yet going to say she's duplicitous, but much like Elidibus, she does seem to selectively withhold information; bear in mind he even does so with regard to his fellow Paragons, where necessary, causing some of them to doubt his methods. If it is true, that the Crystals have to be rejoined somehow to stave off inevitable instability, that may also motivate some of the Ascians, such as Elidibus, to be devoted to reviving Zodiark.
I think that'd be pretty neat and tie in with the role he played in the Warring Triad arc.
I'm not convinced he'll go down that way, yet. The WoL was able to best Zenos and possesses the BoL over and above this, and still Elidibus was able to hold his own, without even apparently invoking the Blessing of Darkness, if Zodiark can even grant such in his current state. If Zenos achieves it, my guess is that it would be through Solus backstabbing Elidibus and assisting Zenos (perhaps in the vein of the whole "family enterprise" thing he joked about, especially since Zenos could be useful as a means to pester the WoL), or through whatever trick Gaius and his posse have - possibly the Heart of Sabik, but if it's that, it would tie to Zodiark and so would work... until it didn't. Either way, I don't think a permanent death is in the cards for him, unless they want to throw the Ascians into disarray and have a more volatile figure like Solus take charge... which is entirely possible. He's good for cutscenes.The problem, however, is whether he will still be inhabiting Zenos body when Actual-Zenos and his Resonant powah finds him. If you truly believe Elidibus will die, then that would be the most obvious method.
And that is the ironic element here. Should they succeed in purging the Empire, they will likely tip the already volatile balance too much towards light.- Gaius, ie. "Shadow Hunter", is actively slaying Ascians. This, ironically, would be a huge scale-tipper towards Hydaelyn for the most part, thus we may need to address it whether we like it or not. That doesn't even mention the past ties we've had with him beforehand.
That's what I am hoping for, to provide a bit more nuance to the story. I'd much rather they did that to flesh his character out more, than have him become Lahabrea 2.0.- Elidibus, whether he is a true emissary, will very likely change his tune with us as WoD's and be presented in a less antagonistic light.
And the question of whether it will involve bearing Zodiark's Blessing, since Hydaelyn's is why we by and large spread light to such a potent degree.- What will be expected of us? Will we have to resort to uncomfortable actions in the name of Darkness? How far have the scales dipped? How far do we need to go to balance them?
Assuming he's not already been compromised by a certain Ascian.- Varis and his clear distaste for the fact that Ascians are the spearhead of the empire. While I find it hard to believe we'll ever ally with him, I fully expect him to stick those glorious shoulderpads into the backs of his Ascian peers at some point. Will we then be able to vie for peace ala the previous politics cutscene, or will he truly go full ham for calamitous rejoining?I enjoy him as a character, so I am hoping even if he is possessed, he'll survive it and return to see the Empire back to more prosperous times. I don't think he simply reserves his distaste for the Ascians, but also for their master, and for Hydaelyn, given his doctrine of putting the reins of history back into man's hands.