Personally, intercommunion seems far into the future. 
Right now, German bishops could issue "guidelines for internal forum," as you say, but for members of their parishes, for Catholics, who are bound by canonical protocol, practice, responsibilities, etc.; issue them to confessors, on a one on one basis. I doubt, however, such protocol would be provided for Lutherans, as if above canon law, above confession, Catholic practice, etc.  First of all, Lutherans would have no desire to go to a Catholic confession, nor assent to Catholic doctrine, etc. I think German bishops are thinking: why give the Eucharist to Lutherans without any of the duties, responsibilities, penitential pieties we impose on or present to repentant Catholics? To allow open communion (i.e., carte blanche) to all Lutherans would be like treating Catholics (into second marriages, with other impediments) like second class citizens, imposing duties, penance, on them, but not on Lutherans. Why is this so hard to get?