What would it take to do an Android app that is modular and where each feature is controlled by a remote server feature flag?

Would I choose something like Firebase, AWS, or a custom server like Alfray or RDRR?

The data itself would likely be json or proto. We would want to have version capabilities.

Notions that become relevant are cold vs hot config, refresh times, networks caching. Also an ETag / checksum system could be used to only send diff/update and minimize network traffic.