I now have whole additional month under my belt (2 months total now
) I have a thought on making it into a Blueprint…
Entity creation/deletion would be inside a script, which is called from the Blueprint’s action.
As you noted using @Blacky 
State Notifications & Actions - Blueprints Exchange - Home Assistant Community … maybe you could collaborate given his expertise in making BPs, and yours in scripting this all together… thus create an Alerts specific BP.
Coming from using several other commercial automations systems over the past 20 years, Alerting and Notifications in HA needs a lot of work and methods like you have designed, and BPs like @Blacky has made, are far more appreciated than I think you may know!