What if the German clubs simply just don't care? What if they don't care about Bayern dominating the league? What if they don't aspire to compete with Bayern? Bundesliga has one of the best attendance in Europe and the world, fans enjoy watching their local teams compete even though they know they might not win the league. They probably have no problem playing second fiddle to Bayern, as long as they keep their fans happy.
And if you institute an anti-Bayern clause, you seriously risk not having some of the best German talent coming to you. Imagine all other La Liga teams had an anti-Barca and anti-RM clause, that would turn off so many players. The fact is most German talent do want to go to Bayern. How do you compete with Bayern? You run a good business, be prudent, don't fuck up like BVB did before, try your best to play good football...
If I were the head of Bundesliga I'd worry about promoting Bundesliga to overseas audience as the lack of competition does turn people away. They are the ones who should be worried.