[1rudeboy]

I’m sure that set-up was good for morale. “Here’s some armor for you, gunner . . . yeah, driver . . . about that . . . .”

[RedMonqey]

I’m sure that set-up was good for morale

Given the churned up, cratered moonscape most WW1 battlefields were doubt these units found much use.

Even in aiding efforts to stop enemy "breakouts" these mounted machines guns would get mired up to it's axles in anything but level, hard-pack roads.

Which were rare

[buwaya]

This was in fact a practical setup at the time.
Both the Germans and Russians used wagon mounted machineguns during the first mobile operations of WWI, and they were useful.
The Germans used them in their Cavalry Divisions in 1914, especially covering the flank of the Schleiffen maneuver, against Belgians, French Territorials, and even against the British at Le Cateau.
German mobile machinegun doctrine at the time was to use them in company-sized groups, opening massed fire at extreme range, 1000-2000 yards, against area targets, manueuvering troops, hasty defenses, especially against flanks. The wagons gave them mobility. Apparently very effective. When everyone dug in this idea had to go away.