The mechs of OPDS: A Field Guide

Similar to their tracked cousins, AAFVs are often defined by the size/weight classification of small, medium and large.  Unlike normal AFVs though, aside from walking upright on legs like iron giants, an AAFV's weapons are fully interchangeable. A soldier without a weapon can always improvise -scrounge from the battlefield. Blessed with humanoid arms and manipulators, an Anthro Mech has similar advantages.

Anthro mechs can hold weapons in their hands, and change them on the fly, but they also feature mounts for additional weapons elsewhere on the body, such as on their forearms, shoulders, or upper hull (back mount), depending on vehicle specs. Back mounts are also useful for a variety of equipment besides weapons, like infantrymen carrying specialized backpacks. Some backpack units are geared for general supplies and materiel, others can boost a particular combat specialty. For example; "power packs" -generators which provide additional strength to a mech's upper body,  ideal for mechs that favor close combat melee weapons.

Similar to their tank destroyer cousins, Mech Destroyers are built to mount the largest guns possible on any given frame, often sacrificing armor and agility to do so. For tank destroyers, the consideration of maximum firepower usually meant eliminating a turret, which restricts the size of a gun's breech, and instead mounting the main weapon directly inside the hull with limited traversal movement. 

MDs have said goodbye to their humanoid arms (along with all the dexterity they provide) and say hello to massive weapons mounted directly to the hull's arm socket. As these weapons are fit snugly against the hull, traversal -the ability to sweep a weapon from side to side- is again limited. Furthermore, as is custom with German and Russian designs, waist ring rotation has also been eliminated for the sake of saving weight, production cost, and excess body size. 

With exceptional ranged attacks, but limited close combat ability, and a miserly armor rating, MDsare natural snipers, best used with hit-and-run tactics. Ambush, however, doesn't come naturally to a walking monster, so conventional mech doctrine decreed that MDs be equipped with reverse-jointed legs, in the manner of birds or theropods, allowing them to lower their vertical stature as much as possible in a crouched position. 

​MDs retain the basic interchangeable components of Anthro mechs (head, chest, arms, and leg section) but the unique situation of combined weapon-arms and reversed legs renders them easily distinct from the other mech class.  variety of equipment besides weapons, like infantrymen carrying specialized backpacks. Some backpack units are geared for general supplies and materiel, others can boost a particular combat specialty. For example; "power packs" -generators which provide additional strength to a mech's upper body,  ideal for mechs that favor close combat melee weapons.

Above is a typical bipdeal conversion of a pre-existing  armored fighting vehicle; in this case, what was originally a US Army M16 AA halftrack, can now follow wherever any other legged vehicle in its combat group may lead. 

The traditional wheel+track setup is still superior for attaining maximum road speed, but when dealing with the toughest terrain, nothing can beat legs!  

Multipedal conversions of tracked vehicles truly found their niche among the pantheon of casemate style (turret-less) tank destroyers.

Whereas a standard tracked tank's mobility and penetration power remain relevant in a battlefield populated by walking mechs, the multipedal conversion of destroyers was a perfect fit. 

Destroyers are snipers -essentially long range specialists that rely on surprise and concealment.

Multipedal TDs can crouch down lower than their tracked forebears, and the added agility of legs enables them to compensate for both the limited traversal, and elevation/depression of their main weapons. 

While AAFVs adhere to the size designations of light, medium, and heavy mechs, German PZFs dramatically exceed that range on both ends of the scale by varying from Dwarf to Super-Heavy. A fact which reflects both the Axis power's ambition, and its habitual denial of logical limitations.    

Dwarf Pzfs, like the Panzer I tank, were only ever intended as stopgaps before German war industry could build the momentum to produce superior vehicles. Most Pzfs in the light to heavy range are undeniable examples of German quality in engineering and innovation. Though as Germany's opponents proved, complexity of design is not always a war-winning trait, when measured against quantity and ease of operation. But until the Allies could rush out roughly equal counterparts to combat them, all German Pzfs enjoyed an interval of domination following their debut on the battlefield.