There is no harassment as there is no real "opponent" though.
Giving pop cap for "achievements" such as having consumed a certain no of goods is a fun idea, but wouldnt it reward the player for just letting time pass? My suggestion of giving pop cap for % of supplied population rewards the player for having a generally "better" city overall, which seems more intuitive.
The + cap for "wonder" buildings however I like, I already planned giving some bonus for prestige buildings like cathedrals and such.
Thoughts?