well being destroyed as soon as target would get rid of the quint problem, but make it too complicated.
i agree with the false keys being false to both players, becasue not only will you have to use 8(7)
and 12(9)
to get it quinted, but you could just get a PA'd diamond shield for just 8
and not worry about the risk
i do think that if you make either of these changes, the cost could be lowered by 1 or 2