When a player is too small compared to others in Civilization, it gets really hard to catch up and more often you just fall further and further behind.
Tech diffusion helps somewhat in regards to tech but empire size is not changed by that.
So what about adding a set of wonders to the game that can only be built if you are small compared to the normal empire size at that tech level or small compared to the other players or in the last half or third of the score list. Or if you could only build one such wonder if you are at war with a seriously stronger opponent and there are enemy units on your territory.
The big players would not be able to build them so it could give a larger boost than normal for that kind of building.
A possibility would also be to focus on giving a temporary advantage like retrieving a bunch of powerful units or heroes on completion or getting a long golden age or a promotion on all existing units (but not new ones).
Tech diffusion helps somewhat in regards to tech but empire size is not changed by that.
So what about adding a set of wonders to the game that can only be built if you are small compared to the normal empire size at that tech level or small compared to the other players or in the last half or third of the score list. Or if you could only build one such wonder if you are at war with a seriously stronger opponent and there are enemy units on your territory.
The big players would not be able to build them so it could give a larger boost than normal for that kind of building.
A possibility would also be to focus on giving a temporary advantage like retrieving a bunch of powerful units or heroes on completion or getting a long golden age or a promotion on all existing units (but not new ones).