I don’t think this is a good idea, but has that ever stopped me from brewing before? Obviously that was just a rhetoric question, but it shouldn’t anyone, because you never know where the really workable ideas lie.
Could we do this with four colors? Maybe, if the format is slow enough. We could use some ramp here. Anyhow, the idea is to use this new Fact of Fiction:
Basically, we are losing Ever After and replacing it with this slower version. We have plenty of big creatures, but we also have a lot of ways to discard them.
With so many ways to discard cards, I wouldn’t mind playing creatures from other colors as well, but these seem the best. Any of the Hour of Devastation Gods would probably be a good addition.