If team bonuses stacked what would be the most insane combination?

Any variation valid. 2v2, 3v3, 4v4, having 3stacked + another bonus, or 2/1/1, or 2/2 stacking.

Which bonuses that are garbage become decent, which ones get worse, which ones break the game?

Meme Answer: Saracen Quad bonus shreds like a Finnish death metal front man.

Slav Answer: Barracks, Stable, Archery Range +20 population.

Duos: 2x Mayans, walls are free.

Also: Modders get on it if it hasn't happened.