Here is an idea I have been thinking about lately:
Printing Press: [Sovereign only or Guild only?] You build a typesetting factory, capable of publishing newspapers.
DDC: 15
Build Cost: 50 GBs
Upkeep: 1 GB / turn
Benefits: You gain a +2 bonus to Agitate within your domain (provinces that you rule directly, or through vassals).
You can ignore up to 1 lvl of modifiers in prosperity levels in the province where the Printing Press is built (in addition to any modifiers ignored by law holdings).