I was just thinking about this today...
If I was in charge of The Walking Dead... and with no idea of what the graphic novel storylines originally did with the character/s... given the departure of Rick (and Maggie?), I think you have to go with your next best lead actor - Jeffrey Dean Morgan.
We'd have 1 season showing Negan's transformation. A promise to Rick. We've learned that before the apocalypse Negan was just a man. He will promise to take over as leader, knowing Rick's dying, but to follow in Rick's footsteps - no more brutal totalitarian regime. We then see time and again, Negan choosing "Rick's way"... right up to the final few eps, when someone close to Negan is killed. Then we have major doubt, as Negan appears headed back toward the old ways... but pulls through in the end, proving himself the new, "good" leader of the communities / show.
That's not to say Negan wouldn't still find methods far from Rick's approach in getting things done... wont still apply some pressure in ways that aren't exactly perfect... but would also leave the audience guessing how far he'll go...
I think the actor would be a far better choice, with no offense intended to Reedus.