Requirement for more power in mapping cases than can be provided by condition or valueMapper transformers

The use case that makes me feel being able to define the default output value on "fluid.transforms.condition" would be useful:

The input model:

{ audio: boolean, sound: boolean; noSoundHazard: boolean }

The desired transformations:

Note that case 3 and 4 are creating the same output value. The question is, at inversion, what this output value should be inverted to?

The expected behavior to invert when this transformation is used in the model relay:
1. If the output value comes from Case 3, always invert back to Case 3 input value;
2. If the output value comes from Case 4,
(1) no change request on the output model: invert back to whatever the original input value of Case 4;
(2) ever have a change request to this special value of

{"audio": "unknow"}

: invert back to the input value of Case 3.

Thoughts?