Say Marvel wanted to kill off Frank Castle and replace him as the Punisher.
They leave it up to you to come up with his replacement.
Here's what I would do
Have Satan decide that since Frank sent so many souls to Hell, he breaks up his soul
Satan finds four people who would be willing to accept the Punisher soul after Satan fucks with them a bit.
Some less than others.
Breaking the four Punishers down into titles
The Father
The Soldier
The Rage
And The Vengeful

Honestly you can never replace Frank, but if you had to?