Scroobal, I am afraid it may not be a new challenge. On the contrary the PAP's job has become easier.
As you said, the people getting sued these days shifted from politicians like JBJ, Chee and Tang to Roy and Alex Au. But unlike JBJ, Roy and Alex are not politicians and cannot milk sympathy votes from what happens to them.
PAP can also claim they have no political agenda behind suing Roy and Alex, since these people are not politicians.