Well it works 
Right now I have the option to hire a playwright firing on FactionTurnEnd, but you can set whatever conditions you want. Note that this is designed only to work with the faction leader because otherwise you have to know a characters name, especially since e_select_character is kind of flawed. Also note that this only works for Kingdoms as vanilla M2 doesnt have the accept/decline scroll. You would have to do it through a show_me.
Click Accept, and you get the ancillary when you click end turn.
Selecting your faction leader and opening his information scroll when you are not inside a settlement gives you the option to fire the ancillary. Because there is a limit on the number of ancillaries I thought it best if you could get rid of him and make room for a better one, and limit the number of super ancillaries.
Click Accept to fire him and he is immediately gone. The e_select works perfectly for this, partially because you already have the character selected in order to open his scroll.
When you are inside a settlement, or in an army with more than one character, you have to select the scroll from here. This also makes the pop up for the choices appear less often, it would tend to get annoying if it popped every single time you opened the scroll to view your character. This way you have a bit more control over how often it pops up.
Click Accept and get the bonuses for holding the plays. I also built in a limit so you can only hold them every 3 turns, so it cant be abused, but that number is easily changed. I also have an idea in mind where if you max out the use of your ancillary he gets pissed and quits, but I havent totally worked it out yet.
Finally I will post the script, you will have to create your own ancillaries, trigger, event descriptions, and conditions for the AI to take advantage of it. Its also quite possible someone will be able to improve this so if you have ideas lets hear them. Its only about 70 lines long so you could easily have a bunch of unique ancillaries without a big performance hit.