Each card has a number of modes defined, and this number of modes will show up in the dropdown box. What each mode means is decided by the card's script itself - it can use the $mode variable to do branching.
However, your concept would require a variable number of modes, while the current engine only supports a constant number. Also, it is not possible to cancel a Play action from inside a card script - once it's played, it has to be played (it's possible to make the card do nothing, though).