I'd be very happy with a female dwarf and qunari as companions! Especially if the dwarf was like Sigrun, I adored her.
Harding hasn't made a huge impact on me yet, but I'd be fine with her returning as a companion. Preferably there would be another significant female dwarf though. So far, we've only worked with three female dwarves: Sigrun, Harding and Valta. Sigrun was the only companion, and only in dlc. Only Harding was in a main-game (rather than dlc). It'd be good to see more than one at a time!
After Justice and Cole, it's time for a female spirit.
Definitely! I'd love to have a female spirit too.
I rather liked Command in Crestwood, but I doubt she'd consent to being a follower rather than a leader.
The Lady of the Forest was pretty interesting too. A very unusual kind of spirit, and one that didn't need to manifest in a human body.
A desire demon would be interesting if she disguised herself in human form like Imshael (but female). I'm not sure how we could convince her to work with us though (and presumably we'd need to keep her true nature secret from the companions). It'd be interesting if betrayal was a factor there. Like unless you could keep a deal going, she will betray you (maybe with the intent of possessing your body?)