I don't think Kanna is going to get shipped with her, it feels like she's more of the 'motherly senpai' for the new cupid to me. Which I realize doesn't preclude shipping, but I don't see that yet.
I honestly don't feel like it's going to be the case, but I really wouldn't mind the coma theory put forth earlier being the ending. They could even do like the wizard of oz movie, have the cupids be people she's been around. Have say Kanna be a nurse at the hospital, Chiyo or Ena be a paramedic that brought her in and the other be a long term patient or something.
The little wing designs on the back or her disguise reminds me of Heaven's Design Team doing a similar thing with their angels.
And by doing a fistfight here, we don't get the plothole of our protagonist not understanding what happens when cupid shoots cupid until the (some time later) of chap. 0. Look forward to seeing where this goes, and if Koharu is tempted to talk to Aki as herself, without apparent oversight.