New ideas:
„Scytale” (simple, yet elegant)
Trigger: Alphabet, Mathematics, (classical & medieval age) city with Library
Thanks to the efforts of librarians and mathematicians in [City] our spy network adopted scytales for wide use. Scylate is a tool used to perform a transposition cipher, consisting of a cylinder with a strip of leather wound around it on which is written a message.
1: Great!: +2

for Library in [City]
“Hygiene”
Trigger: unhealthy (?) city with Monastery (before Sci Method or Medicine)
Monks are preaching about importance of cleaness among the citizens of [City]. There have been no outbreaks of epidemy since then.
1: It’s good to know monks care for both spiritual and phusical purity of our citizens.: +1

for Monastery in [City] (this bonus should be removed after discovery of Sci Method)
Solver, is it possible for event to change a land unit, so that it does not show it’s nationality? (Like a privatter). That would make quite a reward for some kind of spy quest.
EDIT: One more idea:
„Auxiliaries”
Trigger: Barbarian unit inside your cultural borders.
It is said that leader of barbarians warband that have been roaming the coutryside is willing to settle and serve [Nation] if he is paid a large sum of gold.
1: Nonsense. [Nationality] mighty armies will crush those barbarians.: Nothing happens.
2: Pay him.: Pay some

. Gain control of barbarian unit.