I am not privy to the technical challenges in running a site like WIS, but it seems like it should be feasible to roll out changes world by world. From all appearances, the worlds seem to run independent of each other. They have proven they can roll out the recruit generation across different worlds. And in fact, I believe they rolled out the new engine across different worlds as worlds weren't switched to the new engine mid-season as far as I am aware.
Thus, it seems feasible to roll out the adjustments world by world. Obviously if there is an adjustment that is making the game unplayable (i.e., player's disappearing, multiple versions of the same player, something else), then that should be rolled out immediately to all. But adjustments to how accurate certain shots are, etc., should be made after the season is over.
It makes for a very frustrating experience when the rules of the game keep changing as we are playing. I can deal with the quirks of a new engine, because, for the most part, the results are predictable. When the parameters keep changing, however, it becomes a game of cat and mouse with the technicians of WIS trying to guess what the next change will bring to my teams.