If that's ALL +Fulham was doing here, trying to make provision for his flock, then I don't see any grave sin here.

I hate to bring up Fr. Pfeiffer again, but Fr. Pfeiffer has done many bad things under the guise of following his own interpretation of God's will. But God's law trumps one's opinion of God's will. If Bishop Fulham can't tend to his Floridian flock without resorting to getting "married", if all his other immigration options have run out, don't you suppose that's God trying to tell him he's wanted back in his home country? What do you suppose any of the saints would have done? Even the mischievous ones like Fr. Miguel Pro? I couldn't picture Fr. Pro getting married on paper, not even for some religious reason. Too scandalous. 
Aren't countless evils done because one is convinced that God needs them personally and they insist that their opinion is God's positive will?