This sort of thing kinda tells me that Scott Buck has no idea what he is doing. Maybe this is just bad transcribing, but regarding the spinoff
First you say you've "absolutely" talked about Hannah and Harrison in a spin-off then later "there have been no discussions about a spin-off". Sooooo, which is it??
The weird thing about it for me is, the plot points they hit in the ending, I have no problem with, in fact I like them, but just the manner in which they were executed was just not good. The fact that Deb's death forced Dexter to re-evaluate his life and live in exile. . . I don't mind that ending, forcing Dex to take responsibility for his actions. . . finally, is a good thing.
I think they were on the right track as far as the overall character arc for Dexter as far as taking this man, who can't feel, then giving him feelings and giving him a normal life, and how that will affect a person. I just think they had to pad out that arc too much and it lost the 'character study' elements.