First, before some of you eat me alive, let me just defend my reasoning for the following ideas presented. Before Dexter's final season began, Showtime boss David Nevin had stated that he would very much like to keep Dexter's franchise alive. Additionally Scott Buck had also made statements that he would help in this endeavor. Click here to read some of their comments.
Then during Dexter's 8 season it was announced that Scott Buck signed a two year deal with Showtime for several projects. One of those projects is an adaptation of New York Times best seller, "American Dream Machine" in which Michael C. Hall is set to executive produce, but also have a smaller 'behind the scenes' like role. It seems more than likely then that we wouldn't be getting a Dexter season 9, but given the choice to keep Dexter alive, it does suggest a possibility for a guess star role and/or cameo down that series line. (And of course there are always the possibility of flashbacks) I think his return would only be effective, if he became something secondary in relation to the first two spin off ideas presented, as he is reason for launching the futures of those characters' lives, but also it would only work if it was something that isn't freely given in the first couple of seasons, or rather something temporary and/or saved for the end.
1. Hannah McKay (raising Harrison)
The character was saved for the tale end of the series, is fairly established, and provided a concept of one cycle ending and another one starting in relation to Dexter's final season's motherhood themes.
But more importantly Yvonne Strahovski is a strong enough actress to lead the series, assuming it would follow Dexter's blueprint of flashbacks, daydreams, and voice over.
Additionally Argentina is similar enough to Miami in that it is ethnically diverse providing an array of people from all over the world, another tropical-city setting, and some Latin American aesthetic. There would surely be parallels to Dexter in that she is an empathetic killer and no doubt there would be people, even Jacob Elway, who may be hot to find Hannah McKay. Plus maybe Hannah will start her own orchard!
An additional twist could be Harrison. In the final season the writers may have hinted that Harrison either may not go unscathed or that Harrison has some kind of sixth sense and/or psychic ability, as has his imaginary elephant was named Dan (Dr. Vogel's son is named DANiel Vogel), he was highly observant catching Dexter in a lie and calling him on it (and when he was even younger, he noticed Dexter's slide box: "Daddy's box"), and seemed more than prepared to say goodbye to his father while also whole heartedly embraced Hannah as his mother. Either way it could provide extra delema for Hannah to have a problem child.
2. An Older Harrison Morgan
Whether we look at Harrison in his late teens/early 20's or his mid thirty's could this series be an interesting contrast to Dexter, but like I suggested above, it would be better if there would be something other worldly about Harrison, whether he might go around solving crimes, or if we go "The Medium" route with him helping various good and bad people save themselves spiritually in some way. By not making him a killer, we would get something fresh and something juxtaposing Dexter.
3. Miami Metro Continuation (Batista, Quinn, Masuka, Miller, Mathews)
This is actually my least favorite of the spin off ideas. I love these characters dearly, but they were good IMO because they were supporting cast. The only way I could see it working is if one of them became a killer, and leaning on finale false spoiler of Quinn here, Quinn might be a character where that could potentially work, but would be most effective if Deb would return as his dark passenger! Otherwise, I think it wouldn't have that same drive that made Dexter so controversial.
4. Young Adult Astor (image taken from here.)
For one thing, I think a spin off featuring a female lead to compliment Dexter's is great idea, but another reason for this would be to bring some kind of justice onto the dark symbolism of Deb, since Astor was often a reflection of her.
I think I would totally watch a series about Detective Astor Bennett fighting crime and getting into precarious situations, especially since I'm sure the series would include Cody as well, which would also keep the Deb and Dexter antics alive.
Maybe she could keep falling for serial killers...
5. Lumen Pierce
It's true Lumen doesn't have the same establishment or meaning as Hannah McKay, but she's a character who's back story is so lightly touched on that it would be easy to add to it and/or question if was the truth at all. She also was a kind of equal to him in a way where other characters were not in addition to being a surviving 'disciple' of Dexter.
For whatever reason the fan-fic that only exists inside my head takes place in New Mexico where her red-headed dorky best friend, Rusty, is member of Setti and is thus obsessed with aliens, and where her undercover work for the DEA gets her nearly killed every season, while she also struggles with being a child stolen and sold into a porn ring, all the while her non biological mother is a US Marshall born and raised in Texas, who gives her a lot of grief over her life style.
Considering that Dexter ended the series in similar fashion to Lumen in breaking a cycle, I think it could be interesting to get to know Lumen and see how well she adjusted.
These are just to throw them out there, but I think they're mostly iffy.
6. You could start with a completely new serial killer. Whether the killer would also exist in Miami or start in a completely new place may have pros and cons. By reusing Miami the spin off would keep the feel of Dexter alive along with the same supporting cast, but problematically how would we not just retell Dexter's story? How would you make this character interesting, likable, but yet not completely be like Dexter? One way could be if the killer is shadowing the Bay Harbor Butcher. Trying to start completely fresh in a new place would kind of defeat the purpose of a spin off, unless someone left over from Dexter happens to move there too...
7. Another option is a Harry and Mathew's prequel that would basically run like a political cop drama.
8.And lastly a few minor characters that still exist as well: Jamie Batista, Jacob Elway, Arlene Shcramm, Anton Briggs. (I would have named Jonah Mitchell, but it appears Saxon may have killed him, as a "J. Mitchell" appears on a possible victim's list on his computer) -But none of these, say for Elway, sound very promising.
But what about you, any of you not too cut up from Dexter's finale to watch a spin off? Any other ideas out there? Feel free to share in the comments section below!