one more, though unlikely to happen, I still feel the urge to write it
The Grazir quest is anticlimatic, their army is formidable, but still well manageable and their shrine...well, it's great for people who love soloing, but: it favors some character builds while it's impossible to beat with different ones, and, most of all, it doesn't make any sense for the king of whole freaking Perisno to invade the nest of the worst beings on the continent alone, and even more nonsensical for those creatures to let him go if they beat him, so my suggestion for more epic finale:
1) either raise the renown requirement back to 10 000 or make it happen once all other factions have been eliminated or after a reasonable amount of in game time
2) at that moment, turn Grazir shrine into new Zann fort, i.e. center of new faction, give them ability to take castles and towns and spawn them thousand men armies (mostly composed of ghouls, worshippers and priests, but also lot of those insane units)
3) make them invade all the land, spread like a cancer throughout all of Perisno
4) watch players fight a new Battle of Enlightement
My point is, there is no real challenge for a player once you are king with a decent sized kingdom, because the ai is very bad at campaigning and strategic thinking. The late game is challenging only if the player imposes limitations on himself, like player not being marshall, having only companions as lords, declaring war on multiple factions at once etc. Since there is probably no way, how to improve ai strategically, only way to provide a challenge is a massive invasion of sorts. And the Zann don't provide that, because: At default, they come too early for the player to be a king of his own kingdom; if you set the date later, they still suck because they are the worst siegers ever, they can neither conquer nor defend castle when the player participates in the battle, their only strenght is autocalc (OP Grazir troops would be much worthier opponents)
My suggestion would also provide a ton of possible epic "last stand scenarios" (if the trigger of the event was date or renown, not elimination, imagine for example joining RotF and then defending Fountain Hall, the last place of light and hope on the continent, against 15000 demon worshippers...)
You are talented enough to defeat quarelling lords and kings and conquer weakened Perisno, but only if you defeat much worse foes, a threat to life itself and bring a new dawn to Perisno, only then you are worthy to keep your kingdom...