Loyalty and religion working with 1.5 is interesting. We are at the 21 faction limit, so as you say loyalty doesn't appear to be very useful.
Is it possible to make the rebels the counter faction for every other or specific factions that had to face large rebellions like Ptolemaioi or Arche Seleukia? For exmaple that if one of genrals is not loyal enough would start a revolt (similar to medieval:tw).