Allow controller field options to control individual controlled field options

This would be very handy but potentially painful to implement.

Example:
Field A has options 1, 2 3
Field B has options 4, 5, 6

If user selects option 1 in field A, say, only option 5 would be disabled (this option only, the whole field could not be hidden). Currently the deepest the module will go is disable the entire field B.