Definitely up for more Rei CR!! I wouldn't mind throwing him at the ghost ritual, since he's canonically sensitive to ghosts/spirits and magic, and has probably been trained to some extent back home on how to deal with them!

I also wouldn't mind him meeting Jubilee, either, since he's Chinese himself (by the way of Hong Kong), and it's probably been a while since he's really talked to anyone about his culture since he's been in Japan for so long