You wont be able to archive the data completely. When companies leave a system then they usually do not clean up. Hence you have a lot open business cases. And as you should know you can only archive data from closed business cases, and only master data that has no usage, which means all transactional data is already archived.
I did such a project 10 years ago and was able to remove about 80% of the data, the rest will stay forever, nobody will ever give you a budget to close all those business cases and make them ready for archiving.
We had recently a huge restructuring project and did this with SLO tools, hereby we defined all data which had to be migrated and identified all organizations that are no longer with us. So we copied and migrated only the active data to the new system while the original data remained in the old system which got decommissioned. This way we could get rid of the unwanted data too.
But this was just a by-product of the reorganization project, otherwise we would still suffer.
Getting rid of data which belongs to inactive companies is often asked in user groups like DSAG, but SAP does not have anything smart to use.
It was said with ILM you can archive even the incomplete business cases, which is probably correct, but it does not remove the data from your system.
Honestly, why should one want to create new data in a company that is gone? If you want to prevent the accidental creation then remove the authorization for those organizations from the user roles.