In my stash of 1/16th old cars I have a 1911 Model T ,a Mercer Runabout and a Rolls Silver Ghost.
The Model T frame could be used to make a wagon of some kind,the Rolls a staff car commandeered by the German Air Service and the Mercer I know not what.
I figure that the possibility of a Rolls in France at the start of the war could be a good one and of course Model T's were everywhere.Besides what German officer could resist driving a Rolls given the opportunity.

(My motto if it could have happened and it fits the storyline ,use it!)
There is quite a variety of 1/16th figures available today for modification so I don't anticipate a problem there.