What the Weapon class was meant to be

Was the Weapon class intended as a frigate, a cheap destroyer, or something else?

It was an intermediate destroyer meant to maximize the output of yards that could not build larger Battle-class ships.

The design let yards unable to construct the larger Battle class build something more capable than a small fleet destroyer. It occupied an awkward middle ground between the C-class-scale ship and the Battle class. Such a design is easier to justify in a prolonged war than in peacetime.