What about based on follicle development?

This is a tough one. For me personally it's

Age > Follicle Development > Weight

I like my girls to be as healthy and well sized as possible so that first clutch is a good one and sets the tone for the next few years for her.

BUT if she's old enough and developing follices but under 1500g I'd attempt to breed her.

I think breeding a female too young and too light can hinder their egg production for the first few years of laying and potentially longer.

Hope that helps