Can Heroku Connect be used as an Archiving tool?

Hey guys, we recently signed up for Privacy center and configured Heroku connect. We would want to archive our objects data to optimize our data storage and reside the archived data in Heroku Postgres database through Heroku Connect and would want to retrieve it back to salesforce when needed. Is it possible? 

I tried data retention policy of type delete on a custom object and configured external object to view the deleted cache data. However, I can only access 20,000 records in salesforce and I can't restore/retrieve the deleted data. I believe that's a limitation. Isn't there any way we can use Heroku connect as an archiving tool or do I have to rely on apps like Data Archiva or Data Connectiva? Please share your thoughts.