Hi Erel,
I understand how difficult could be to introduce a different approach on a well-established product like B4A, so it's understandable it deserves all the time for a thorough and deep thinking prior to take any decision.
If at any time you will feel ok to change the starting approach, may I suggest the introduction of a separate "Process only" module?
That way we will have a single point for process global vars, a process_create function (and maybe a process_destroy one) common to all applications where activities, services and other modules will live independently (sort of) but at the same time could count on the existence of that common ground.
I don't know if Android permit it, but with the above scheme we could even have an app without any Activity (I'm thinking about a pure service that many apps could use once started).
Well, I am pretty sure you don't need my hints and eventually will find a proper way to manage a sharable evolution for your great products.
Umberto