Your points in faction flavor are quite valid, at least in my eyes.
On the UKF lacking basic tools: I would remove the mortar pit and add a 3' Mortar team (start with a G.W. 34, decrease fire rate, increase range). Next, to all of their weapon teams (or perhaps just the Vickers and the 3' Mortar), I would add a toggled Entrench ability that allows them to set themselves into a mini-emplacement.
This emplacement would have the hitbox and model of a USF Fighting Position. It would have the HP of a sandbag (easily de-entrenched by mortars or tank fire) but would make them much more resistant to small-arms fire.
![Honor icon](/images/replay/honor_icon.png)