I actually would like Typhoid Mary to show up eventually, but I wouldn't be shocked if she gets yoinked by a different Defenders hero. That said, consider that Bullseye's really big iconic plot is a no-go, since they are already doing the Death of Elektra otherwise. So, using Bullseye means coming up with a different angle and focus for him.
Personally, I am inclined to ditch the Fisk connection largely, and make him the Joker analog: an evil, sadistic serial killer who rampages over the city, and only Daredevil can stop him. Make the Bullseye story line structurally a serial killer plot, with your victims and taunting messages to police/Daredevil and focus on the killer's psychology. Its just that, unlike your typical serial killer, he can actually get into meaningful fights with the hero.