Have you had a look a this:
https://www.b4x.com/android/forum/threads/b4x-cloudkvs-synchronized-key-value-store.63536/
If you have the facility that you need to implement this, it works brilliantly and will address most if not all your needs.
Take a careful look at the code and how this server works. Several of your ideas are addressed in this tutorial. Personally (an untested theory) I feel that an App user will start doubting your app if you are running several updates over a period of time, so your most ideal situation would be to place an app on the store which is properly and then try as far as possible to do updates etc from a back-end server.
Another alternative is to build on @DonManfreds post above by using PN's or even using one of the MQTT principles - as the English would say "It's Horses for Courses" - read your environment, choose a strategy, then choose the correct tools and build your solution.
Enjoy !!