Let one specify a spawner instead of amethyst as a destination block for mind flaying, and choose any entity for this. This would be a very good other use for the spell, letting people make spawner farms for mobs not naturally occuring in spawners.

could maybe be done with the new 1.20 flay any entity stuff. might require a way for a block/block entity to receive what entity was flayed into it. Otherwise sounds like something good for an addon.