Product events with i.e. IObservable before product is saved and after.
(Be able in event before save make a complex product validation and show a validation error for the user.)
maybe also other events like product deleted (which will make it possible to add soft delete or add an seo 404 redirect),
We have create issue on github https://github.com/VirtoCommerce/vc-community/issues/493 and schedule this task in near future. Thanks for suggestion!