Some ideas for events and decisions (sorry for the broken english, it is not my first language):
1. After choosing ideology, players may choose whether to purge their royal family or creating constitutional monarchy. The second decision would increase wealth and culture better than the other plus giving them extra magistrate. Purging royal family would increase population and production, also gaining a great artist, musician or writer.
Note : This event may also be trigerred when player gain the capital city of another player, purging other players' royal family would increase wealth 30% and production 10% also enter to the golden age for 10 turns, marrying local nobles to foreign royal family would increase happiness or decrease happiness permanently, there is no need to build a courthouse for the controlled capital city and increase culture.
2. Possible events and decisions for constitutional monarchy :
A. Royal fiancè : choosing spouse for crown prince / princess either a foreign royalty, a noble or a commoner. Foreign royalty increase wealth + foreign legion or other foreign units, noble increase wealth + culture, commoner increase culture and a magistrate.
B. Royal wedding : choosing lavish wedding or simple one, both increase culture and entering to golden age, however lavish wedding may cause revolt through the whole country although it increases culture a lot. Revolt will trigger purging royal family event. Need a magistrate
C. Royal succesion/assasination : no male heir to be found, choose either to break tradition by giving power to the princess or giving it to the closest male relative from royal family. Choosing princess will increase culture, choosing male relative will increase production. May trigger revolt.
D. Identity crisis: during medieval era, royal have to choose the identity of the country, choose what kind of tradition the country should get. Choosing commerce identity will increase wealth 1%+ 1 caravan, choosing military tradition will increase production 1% + unique military unit, choosing art and science will gain either great artist or great scientist.
E. Royal religion : choosing religion domination e.g for christianity choosing presbyterian, baptist or lutheran; for catholic choosing dominican, jesuit or anglican ; for muslim choosing sunni, shia or suffism, etc.
3. Possible events and decisions after purging the monarchy :
A. Celebrating independence day : choosing lavish or simple, similar effects to royal wedding event
B. Party leadership : choosing dual parties or multiple parties parlimentary system, similar effects to royal succesion event