Franks : Mongols : Magyars
Pick 2.
This game isn’t going to last long.
Celt + Slav.
Faster farming and faster woodcutting
Siege fires faster, workshops produce faster, siege is discounted and has an upgrade to HP
Infantry moves faster and has an upgrade to provide blast damage
Castles cost some wood now (even easier to spam with the celt gather rate bonus) and can be upgraded to fire faster
The ultimate BF civ?
Insane eco with completely OP siege and bonkers infantry to back it up.
Cheap faster-firing castles to lock down positions.
Good luck pushing
Goths and Aztecs.
The infantry spam will never end, now featuring actual economy bonus and eagle warriors.
Alternative would be Goths and Slav for modest farming bonus and druzhina huskarls.