It's a "plain clothes" action series with less eldritch bolts solving lots of problems. Strange wears a coat. Fans will want to hang me.
1: Sword fights with monsters in central Manhattan.
Sword fights are cool. The Black Knight is the main sword-wielding Marvel hero (although Paul Cornell is working to fix this with Captain Britain) so there's a vacancy for a guy who carries an enchanted swordcane and keeps fighting monsters who wield medieval weaponry.
Monsters are cool. I feel this needs no clarification.
Sword fights with monsters are double cool. Put them in an anachronistic location and this increases. So this is the book's main action beat.
2: Jennifer Kale getting a clear particular ability that leads to lots of story hooks.
Jen is just about as muddled in her portrayals as Strange himself, and doesn't have a cool superhero name that ever worked. So I'm going to keep the ancestral connection to an occult tradition and her being a college kid contrasted with Strange's grown-up-ness and politely overlook everything else. As for her specific power, I'd make her a seer. Precognition and postcognition mostly triggered by touch, seeing through illusions. Obviously useful, and it gives her a reason to play Buffy to Strange's Giles.
3: Jen and her friends being funny, charming and a little bit heroic.
This lets me write likeable "normal" characters as well as Strange being high-minded, and to have completely unpowered people help save the world.
4: A likeable ordinary cop who sometimes has a hard time dealing with what her adviser on occult crime tells her.
And yes, she's rather attractive and close to Strange's own age.
5: A secret cabal willing to do horrible things to save the human race.
Strange doesn't do much spontaneous spellcasting, but ritual magic is easier to cloak - and this cabal is at work in the background, preparing something that they would call a necessary evil. Whether they're right or not is a question to be addressed when Strange finally tracks them down.
6: A major recurring role for a ghost.
Ghosts are cool. I feel this needs no clarification. And there aren't many major recurring ghosts in the MU.
7: Doctor Strange versus The Hulk.
Get the good Doctor out in the wider universe instead of having him visit it when someone in another book has a magic-related problem and needs a consult. Also show him fighting an unstoppable force with his wits, and demonstrate why he's reluctant to throw spells around.
8: A possessed train thundering towards Grand Central Station.
Big weird threats caused by the upheavals of magic, endangering innocent people.
9: A voyage to the Underworld.
This could be a crossover to bring back a deceased MU character and earn the resurrection big-time, or it could involve someone we don't know.
10: Sea serpents leading to a lot of Jaws references and a teamup with the Fantastic Four.
Monsters are cool. It also gives us the chance to have Strange discuss the physics of magic and answer some reader questions.
11: A city being magically warped to how it was over a century ago.
Another big weird threat, which also allows for lots of time travel humour. This is one I've used before, and making the effect spread creates a serious worldwide danger as well as an excuse for corset jokes.
12: Dormammu as a huge apocalyptic threat, in big strange Ditko worlds and on Earth, who our heroes resolutely refuse to be scared by.
"Your head looks like a match."
13: No zombies. Instead, a small army of skeletons.
No zombies because they're played out as MightyGodKing notes in his Legion pitch. Skeletons because Ray Harryhausen rules.
14: The worshippers Strange would attract and how he deals with them.
Warren Ellis's runs of Hellstorm and Druid both played with this idea - someone who can learn superhuman abilities is going to have people trying to learn from him, and someone as powerful as Strange is going to be worshipped. And there's only so much that a polite refusal can accomplish.
15: The mystical secrets of ancient America.
Monsters are cool. Monsters like Manitou and Wendigo included.
16: Ninja who can walk through shadows.
This is mainly an excuse for a surreal fight scene.
17: A doomed romance between a boy and a ghost.
This feels like a subplot, or a single issue. A quiet little romantic story that still falls under Strange's remit to try and help.
18: A small-time occult artefact dealer who's just helpful enough not to shut down.
Allows for more plot hooks due to the artefact market and a "which way will he jump?" cliffhanger.
19: Dragons in Jamaica.
Dragons are cool. Jamaica lets me sneak in a magical explanation for the destruction of Port Royal, and also some pirates.
20: Jen teams up with Electro to save Rhode Island.
A wildly inappropriate teamup that demonstrates how Strange (and now Jen) deal with different kinds of problems than most superheroes, and are willing to use different methods.
"Hey, you! C'mere! We have to save Rhode Island!"
"Uh... I'm a bit busy robbing this bank here..."
"Yeah, well, we all have problems. Come on!"
21: A Deluge.
A potential crossover event starting in Strange Tales. A not-apocalyptic-but-certainly-bad mystical superstorm.
22: Clea, at her most weird and powerful.
The return of a beautiful interdimensional princess, naturally, at the worst possible moment.
23: Seventy ghosts appearing in a single night.
A murder mystery, times seventy.
24: Baron Mordo Saves The World.
The old "villain saves the world because it's where he keeps all his stuff" story, I freely admit, but forcing Strange to work with Mordo - who I see as a lazy cult leader surrounded by worshippers (see point 14) and using magic for his own entertainment and selfishness.
"Call it enlightened self-interest, Doctor."
25: Rat Kings trying to take over Brooklyn.
A creepy little story.
"Look at the numbers of us compared to the numbers of you."
26: A Minotaur.
A creepy big story. (Probably not Rintrah the green Minotaur who was once Strange's apprentice.)
27: Vampire Nazis.
Do I need to explain this one?
28: The Screaming God.
Ancient unknowable power which could backfire on whoever tries to use it.
29: Magical unpredictability that creates good and neutral events as well as evil ones.
Like teddy bears protecting children from monsters in the closet. (That example's a bit too Little Fears, but having a teddy bear turn up at Strange's house asking for help appeals to my sense of the bizarre.)
30: The death of the world.
An apocalypse starting right here, tying in to the strangeness of magic, the cabal, the ghosts, the Screaming God, all the previous crossovers and more.
Did I mention the death of the world?
Bonus points to anyone who can spot which of these I've already more or less done in The Watch House.