ZeroNet (distributed TOR hosting): https://zeronet.io https://github.com/HelloZeroNet/ZeroNet
and either: SecureDrop: https://securedrop.org https://github.com/freedomofpress/securedrop
or NextCloud: https://nextcloud.com https://github.com/nextcloud
Though basically you're just routing .onion at a bucket.
Another thing to look at would be building on https://libcloud.apache.org/ https://libcloud.readthedocs.io/en/latest/supported_provider... or https://jclouds.apache.org/ https://jclouds.apache.org/reference/providers/
And providing a storage target. Though you have to consider the possibility of seizure of the host[s] by the service providers state.
See: https://www.deepdotweb.com/2017/06/10/french-police-seized-t...
https://www.bleepingcomputer.com/news/security/french-police...