The Oh My Ghost opportunity is not banned so you can bring back a spouse that way.
Spouses don't have to be a different life state when they move in (Example: Samoht's story) but they do have to be their final life state before you ever have children.
@hazelnut - When your heir is YA or later, you can then move in the ghost to be a spouse and cake him up. Metro and I are still discussing the founder part but part of me feels that in the spirit of the challenge, your founder would have to be his/her final life state at the completion of the tasks. When Metro becomes free, he'll let me/us know his opinion.