On Owner deletion, all dashboards created by him should not be deleted

We recently had this happen to us (luckily in a dev environment). In our case the user was deleted through an API call, not the web app. A resolution that only changes the prompts experienced through the webapp would not be sufficient guardrails. I'd prefer making the default behavior to transfer ownership to the sys admin or allowing for dashboards to be ownerless and provide the ability for an admin to change the owner on an ownerless dashboard.