Have a look at the enclosed photo. Taken in 1921 it shows the floor of a company founded by Joseph Vollmer (yes him again) to manufacture agricultural tractors. This company eventually grew into Hannomag and is still around today. The first batch of tractors were assembled by hand and the guys on the right of the picture are doing just that. Now look at the left hand side of the picture, those guys are not assembling but disassembling - see the cold chisels and engineers hammers for knocking out rivets. It looks as if they are taking apart A7V traction units, presumably to provide parts for the tractors. Further back an engine is being removed from something.
Re reading the Versaille treaty this is legal and could be carried out overtly - the terms of the treaty forbad Germany from making or importing tanks or other armoured vehicles but not selling old ones! It states that existing war material must be destroyed or otherwise rendered unuseable (my italics). Converting the remaining parts of uncompleted A7Vs and/or oberlandwagens into agricultural tractors would fullfill this (especially if exported). Interesting?