Worth keeping in mind that military ideas which don't work get changed out FAST.
The urban poor armies displaced landowner armies extremely quickly.
Why? The same reason the landowner armies were much more common than a full time warrior army past the tribal stage.
Numbers.
The Urban Poor can be recruited in great numbers very cheaply, requiring only several months of training, compared to the landowners, who needed to be trained from childhood to use a bow. Furthermore, the Urban Poor are trained in the modern way, one trainer directing dozens of individuals at once, which meant in turn that drill and discipline become more significant parts of training.
As a bonus, we're getting nearer to pikes! After this transition we'd be able to pack Crossbowmen behind Pike Hedges.
It's sort of like archers bringing their own forest.