Yeah your right there, the SPQR and the Papacy don't feel complete. I tried playing as the Mongols to see what would happen and it started on the HRE's turn and stayed there.

I heard it's possible to install a script where an adviser would appear and if you clicked on the show me how button it would give your faction to the AI and let the AI take turns until for example the Mongols emerge and then it would let you play them, anyone know how to do that?