I could guess that in some cases LH will cancel outbound flights from FRA and MUC to strange places so that the planes are not stranded at these "odd" places during the strike.

I think that right now some unlucky LH employees in charge of schedules are pulling some overtime to minimize the impact as much as possible. Last time there was a strike it took 48hours to return to the normal schedule after the strike was over. So even if you plan to travel on or two days after the strike you might be affected.