If anything it looks like they're drawing on many different FFs, and I would agree that they don't tend to go for outright copy/pastes so much as inspiration MSQ-wise.
Anyway, I am not too wed to the whole idea of Zenos comprising of Azem shards, again mostly because I don't like him - it just seemed like something they could plausibly pull off. If it turns out not to be the case, so much the better. As you say, he has ruled out redemption and more than that, Yoshi has said they don't intend to do half-ways with purer villains like him... so I'd rather they stuck to it. Fandaniel is hinted at harbouring some manner of secret, so they can pursue a deeper story in that way, as opposed to redemption arcs.
I agree, she is a closer fit.