Just out of curiosity why do we not simply require that an alternate Community business owner be implemented either right before that user (any Community business owner) is removed/deactivated from Connections Cloud or when Communities are created.
On-prem provides a wsadmin command which designates an alternate Community owner for all of the communities in which a specified Community owner is in ownership.
The details of this task usage seems to fit this scenario:
About this task
If a community owner needs to transfer or share ownership of their communities and subcommunities, for example if they are going on sabbatical or leaving the organization, you can add another user as an alternate owner of those communities and subcommunities. When you assign an alternate owner to the communities and subcommunities owned by a particular user, you can choose to leave the existing owner in their role as owner, or remove them from the community and subcommunity membership.
Or an option can be added to Communities UI allowing Community creator to designate an alternate Business owner.