An F3-layout Dreadnought would reset the battleship pattern

How would other navies respond if HMS Dreadnought had been completed with the F3 all-forward layout?

They would probably build their own versions, especially if the layout also delivered useful speed and heavier guns.

The consequences depend on gun caliber and speed, but even a nine-gun 12-inch F3 arrangement could produce a ship of roughly 23 knots. Other navies would probably copy the layout because it would redefine what a dreadnought looked like. It would also satisfy Fisher's desire for six guns firing forward, connecting turret arrangement to tactical preference and international competition.