I am rather sure that test.support is going to remain private.  So the concrete proposal should be to move them into the unittest package somewhere, perhaps in a new unittest.utils/support/helpers module, for battle-tested helper functions.

I strongly suggest that you make such a proposal on the python-ideas list, both to get support from users and also from a coredev that might review and merge if approved.

A new module should require a PEP, which should include some criteria for what might go into such a module.  What some coredevs will rightly fear is an avalanche of proposals to various person's favorite thing from test.support, or even elsewhere.  Why these 3 things and not other things or even everything?  Take a look at PEP 1 for what should be covered even in a pre-PEP.