I agree that's a problem and something needs to be done. Removing invisibility from the scheme is a sad workaround, but if the problem is widespread enough, it should probably be taken into consideration, at least as a temporary measure until a real solution exists.
With the way WA currently works, it's impossible to completely prevent a local user from reading the worm location data during invisibility. With current cheat systems, it's probably done as a side effect of getting the game engine to play the game as if it was playing a replay. However, even if that was somehow prevented, the worm location data would be trivial to track and display positionally on-screen with an external program for an experienced cheat programmer.