Hi,
I’m afraid for this you may need some sort of a custom code. I suggest using the asp_results hook, as it serves mainly for manipulating the results before display.
The rough outline of the code is, that you loop through the items, gather the variations by products in an array, then check the occurences and remove the unwanted items accordingly.
I usually suggest a custom code where I can, but this may be a bit more complicated than that.