Good question.

The moral culpability derives from the act of the will. Everyone “falls off the wagon”, it is why the sacrament of Reconciliation exists.

This situation is no different than any other sinful habit which one is fighting.

“Amoris Laetitia” itself says nothing that conflicts with that, despite the personal opinion of Ms. Zagano and some participants in the discussion.

The difficulty arises with Footnote 351 to “Amoris Laetitia” which can be interpreted as a “nudge, nudge, wink, wink” to divine law.  Either this Pontiff or the next is going to have to clarify that.

So Familiaris Consortio, and the sacrament of Reconcliation, already effectively provides for Communion for couples who are trying to do the moral thing.

Where the problem arises is that you cannot receive absolution if you already have formed in your will an intention to NOT live as brother and sister.  So, if you take actions which will certainly result in coitus your confessor may question your sincerity.