i have an interesting idea with castings. It would implement an element of "defense" and make the game more competitive.
In addition to pop up keys, poison and apples, there would be a pop up lock. If you click the lock, you can play the lock at any time on any particular player. If a player gets locked, he can no longer get any checks or play any challenges until he gets a key to unlock the lock.
That way if someone has like 5 keys 5000 checks and high challenge scores, for example only, if I grab the lock, I could use it to level the playing field for a little bit, or if I 'm alligned with him, I could use it against his closest competitor. It encourages alliances in castings as well, something that castings could use.