While this works, note that this is dangerous, because hybrid cards aren't shown. For example, if I apply c<=rw on my sealed pool, which also contains [[Dovin, Hand of Control]] and [[Kaya, Bane of the Dead]], neither of them are shown even though they could easily fit into my deck.
SHUCKS! You are totally right. Hm... I wonder what the right filter for that would be. "Castable with"?