Sword fighting and tennis racket swinging are similar any many respects.
Several basic strokes, several less used alternative strokes, and as many reposts and replies....
What is the ideal balance for a sword, or a sabre, epee', foil?
There is none! It's based on strength of handle to hilt to blade, since most cutting weapons are made of solid steel of some kind. Balance is determined by usage. It's abliity to not break, strike hard, defend against hard strikes.
But tennis rackets are made of composites, and as such, can have enough strength to make balance a completely different factor. Tennis racket balance is solely to aid the player, not for fear of breakage.
Nobody knows what balance is ideal for the PLAYER. Baseball bats are head heavy, hockey sticks slightly head heavy, golf clubs definetely head heavy, while tennis rackets are mostly head light in heavy weight rackets, and head heavy in lightweight rackets.
Maybe SW has everything to do with it, or at least more to do with it.