You don't need to store the full old configuration anywhere other than as part of the current configuration. All you need is a list of IDs that existed in previous configurations. Something like:

  current_tables {
    TableA {
      Column1[string]
      Column2[bool]
    }
  }
  removed_tables: ["TableOld", "AnotherOldTable", ...]

Depending on your ergonomic preferences, you could also accomplish that by keeping the old table configs and adding an "is_deleted" flag. And once you've done one deploy, you can delete all the old tombstoned configs.