As Sinan pointed out, your own playstyle and maybe even "houserules" per se are what expand the game into something more. IMO makes the game much more fun and enjoyable to play. Trying to play 'good little catholic' and appeasing the pope is fun, and when you do he never bothers you for attacking other catholics. In fact, most of the time if you are attacked by others he warns them instead of you, 'good little catholic'.

Any kind of little house rules you can think up and abide by to make the game more challenging and fun.

Tschüß!
Erich