I considered
Arcane Adaptation but 4 copies would be required for consistency and I felt that it consumed far too much space (which is why I trimmed the creatures to
Crested Sunmare and Vizier of the Many Faces who enter as horses).
Ixalan's Binding is actually a great option that I've been considering for a short while; it will most likely be in the main deck, otherwise it will certainly be in the side.
I understand that about
mirage mirror. It isn't ideal, but it makes for an easy 3 drop that could be a decent blocker and wouldn't fall victim to
Fumigate (unless a make it a creature, but that would just be an awful misplay).
Thank you for the recommendations!