These are the changes I've found enjoyable. I'm not attaching a file, because you can DIY. Basically, I wanted a more challenging Regent level game (that is, a game in which the AI didn't need to cheat) and found the following added to my gaming experience. I obviously do not like getting to the Modern Age too fast...
Tech changes:
Increased the map tech factor by 1/5.
Increased cost of all essential techs in the Middle and Industrial Ages by 1/3.
Unit changes:
Changed Privateer to 2.1.4.
Changed Barbarian basic ship unit to Privateer.
I'm contemplating more changes, but these are the ones that have been successful thus far.
Tech changes:
Increased the map tech factor by 1/5.
Increased cost of all essential techs in the Middle and Industrial Ages by 1/3.
Unit changes:
Changed Privateer to 2.1.4.
Changed Barbarian basic ship unit to Privateer.
I'm contemplating more changes, but these are the ones that have been successful thus far.