As a Finnish guy I have to raise a hat to this and chuckle. I've not heard many take up an idea like this, though it is interesting, adn quite fitting considering that the "Mistress of the North" was a villainous woman throughout the entire Epic, at least in the eyes of the heroes of that Epic.
Anyhow, I'll wish you luck, I might be interested but I figure that in this case you are going to be looking for a female player for this matter. Still, wanted to tip my hat on the idea as a Finn, at least, especially given that the idea intrigued myself as well.
Also, if you can find it there's a roleplaying system called A.N.K.H out there somewhere.
Adventures of the North, Kalevala Heroes.
That is, Kalevala is the name of the Finnish epic that the above mentioned Goddess is a part of. The game is pretty old and scarce, and figure the rules system would be a bit of a headache to pick up, but that said it would provide you with a load of gaming material. Given its out of print (to my knowledge) it might even be available somewhere for free. Cant promise that, haven't looked in ages.