Wonder if the female character will be Trubel. Then again it could be a prequel and feature Kelly and her adventurous back story. But assuming they don't ignore the epilogue the spin off would be 20 years later. The female character could be Diana who is following the path of the Grimms. That would make it possible to have the original character and not have to use the original actors.
Embrace your inner Biest..... We all have one