Thank you for the detailed feedback, doesn't happen so often here as most people post for the sake of posting.
Bayern Munich does have great players who can take over the needs in the offensive game, but you can see that as soon as Harry Kane is out, they don't have this lethal striker. The problem is that you can never have two Harry Kanes or two whatever great striker because they wouldn't sign a contract if they know that the point is to leave one of them sitting on the bench. But I fully agree that there must be a plan b. You can't play as if Kane for Bayern Munich or Lewandowski for Barcelona is available forever.
Bayern Munich will still win the Bundesliga I think although they got beaten by Mainz, but this is more like Liverpool losing a game and then winning the next one. Too bad that Bayern Munich doesn't get challenged harder.
I completely agree with you that Bayern Munich depends a lot on Harry Kane ability to score goals. They have good players but they do not have another striker who can score goals like Kane. You are right that it is not realistic to expect two very good strikers to play together because they would not want to sign contract if they knew they would be sitting on bench.
Having backup plan is very important because teams can not always rely on their best players being available. Bayern Munich recently lost to Mainz which was disappointment but I still think they will win Bundesliga. They are very good and even when they lose they usually come back stronger.