In Denmark, Norway and Sweden, each for its own reason, there are minority governments.
CDU/CSU with or without FDP should attempt a minority government. Then, seek enough votes from the members of the other parties on a case by case basis. This can be done.
The problem FDP has (and also CSU) is appeasing the Greens on immigration and fiscal policy. But, since she has verboten AfD, she cannot form a coherent majority government. So, minority government is the best option.
The Establishment must stay in power at any cost.