re Taharah between a man and woman touching via an object, that are more critical here than Tznius
Considering that this thread is not talking about a husband and wife*, I’m forced to ask what taharah issues are there? In the absence of the BHMK what Tumah/Taharah issues are relevant? Do you not take objects from your mother’s hands or the hands of your teenage/adult daughters? If there really were Taharah issues, then you would have problems with immediate relatives as well — which I *highly* doubt to be the case.
The Wolf
* And even with a husband and wife, the prohibition on handing objects back and forth while she’s a niddah has nothing to do with Tumah/Taharah, but rather as a harchaka so that they shouldn’t come to be intimate.