It's not really usable here. Even people who are unaware that the Aunt
Jemima advertising character stemmed from a stereotype would see it as less of a name. Instead, people would see it as yet another product name like Kraft or Nabisco (I know Kraft and Nabisco aren't first names, but I'm just using them as an example).
Jemima is a beautiful name, so it's pretty sad that it became associated with a Mammy archetype used to sell pancakes. I mean, they could have picked a much less lovely name like
Hephzibah or Keren-Happuch.
However, outside of the US and Canada,
Jemima seems to be acceptable as a first name. It's fairly popular in England.