May I suggest that one solution to the "Great Library" dilemma? You use not one, but five "Great Library" wonders:
1. The Stoa 400 BCE (Greece) - expires with the discovery of Republic.
2. The Great Library 200 BCE (Egypt - requirement: papyrus) expires with the discovery of Imperialism.
3. Nalanda University 400AD (India - requires Buddism) expires with Feudalism
4. Islamic learning 700AD (Arabs & Persians - requires silk road* and Islam) - expires with The Crusades.
*That would be because the Chinese discovered paper (required hemp) in the first century AD or before but it was only made available to the Ottomans in the 7th century and wasn't discovered by the west until nearly 500 years later.
5. Printing Press 1400AD (Europeans - requires Reformation) doesn't expire.
In this configuration, libraries, monasteries, and harbors would provide 'normal' education benefits, while religious buildings: temples, churches, mosques and stupas, could provide small education benefits since priests usually had to be literate. 'Event' techs such as Paper (East) and Marco Polo's Travels (West) would provide 2 civilization advances each.
The main advantage of this scheme is it follows actual history and spreads the GL benefits to each civ group, but in different eras.
I realize this doesn't really match the tech tree in your excellent scenario but, well, you asked.
Edit: On the other hand, I like your solution better; it has the advantage of being waaay simpler.