Antares re-released their microphone modeler,
which is on sale now. It irritatingly requires an iLok, so I won't be getting it - I hate the idea of my critical software being at the mercy of one easily losable dongle.

But I digress...
It obviously can't create signals where none exist. Rather, it emulates the
response of a number of classic microphones to a signal. The legalese:
This product is not guaranteed to produce, and will not necessarily produce, audio results that are consistent with or match audio results that could be achieved using any of the referenced microphone models.
In the end, things like this are just a tool. If it gets you closer to the result you want, great. For $30 (on sale) it looks like a potentially useful thing to have.