Are you, the Devs, having issues with the natural improvement of stats through activity as a result of thinking it too complex for the players or too complex for the code?
You say the problem is technical, but then say that the issue is the complexity of it for players.
If it's too complex for code, there's no use in continuing. If it's merely the opinion of complexity for players, I would like to continue trying to convince others that it's not.