On the Hybrid talk, I'm mostly positive.
I think Denji not being able to die is a great part of his character and the story.
I loved the return of Katana man, it was excellent and I hope he returns again. As for Quanxi, her return felt underwhelming and pointless so far, maybe it is a set up for some future event, but she wasn't necessary.
I'd love to see Barem and Sword Man again, they were great and I feel they could have more to do in the story. The fact that an asshole like Barem could just come back at any time is such a nice plot point.
My only grievance is Reze. Her story ended perfectly and I wouldn't want to see her return. However, I also got the read that if she was ever "free" again, the first thing she would do is look for Denji. So my only interpretation of her situation is that she is locked up somewhere. But I can't help feeling that she has to return eventually, even though I wouldn't want her to.
If the series were to end without her return I'd be frustrated, but if she was to return I'd probably be disappointed. It's a no-win situation.