Allow the People taxonomy to delete terms automatically when removed from AzureAD
The People taxonomy automatically adds new terms for term sets like Department and Job Title when a users details are updated in AzureAD (manually or via an incremental sync) however terms are not automatically removed from the taxonomy in the popular scenario of a department name change or branch closure (its common for a remote branch to be listed as a department).
Without this its impossible to use the Department term set as a valid source of truth within business solutions within O365 without devoting manual resources to triage old department names. Organisationally most businesses will not want users being able to select an old department. While this would impact editing an item where the existing Department value no longer validates successfully against the term set an obvious solution would be to depreciate any old values. If this is done automatically you can save most businesses from needing to build their own custom solutions. Considering that most solutions are going to look almost identical automating this in O365 would probably be enough that most organisations would not bother creating the 2% extra functionality that gold plates the functionality.