It would be great to be able to model for either my death, or my wife’s, separate from the end of plan.

I can see a couple ways of doing this: 1) a new built-in milestone that allows for picking a death date separate from the life of the plan, and then that date would interact with other items on the plan. For example, if I have modeled me working until I am 65, it would be good to model what would happen if I died at 60, so the new milestone should stop my salary, trigger life inurance, etc.
2) Allow incomes and expenses to have multiple Boolean criteria. In this case I could make my own custom milestone to model my death age, and then for my salary, for example, it would be until retirement OR death.

Additionally, having individual death dates allows for separating us from the life of the plan so we could more easily see what kind of legacy we would be leaving for charitable donations, family trusts, etc.