I think I'd be happier with periodic graphic novels based on MOTUC. I know this isn't really addressing the question, but it would be much easier to keep up with the cardbacks and not veer away from that story in Graphic Novels. With animation you have to make quick little stories, and do so many episodes by a certain time. I've never seen an animated series based on source material stay true to that material.
If anyone on here reads Astro City, I can imagine a MOTUC comic done in that style being really good. Maybe a story about a citizen of Eternia, or a member of the royal guard being the focus for a story, so that we see the world of Eternia, and it includes the heroes and villains but creates a more realistic feel (and avoids making claims that future cardbacks have to either adapt or retcon). And like Astro City, you could have one GN about current times, then have one about Preternia, and move around wherever the writers want.