The titular mecha known as Modular Assault Vehicles got their start as simple M.M.Vs (modular mining vehicles) but were quickly re-purposed after their potential for mayhem was realized in the hands of some disgruntled Europan Miners. Now, both the E.D.F. and the Jovian Revolutionaries employ modular mecha for a variety of purposes and with parts ranging from cobbled-together mine-layers to specially engineered military-grade Railguns.
Origin of the M.M.V.
Mining equipment on Earth has long been somewhat standardized- heavy-duty steel frames mounted with hydraulic motors and large all-terrain wheels, each vehicles designed around a single specific task- pushing, scooping, picking up, etc. etc. With each different task requiring a separate multi-ton vehicle, the economics of planetary mining didn't add up for any location that didn't already have a significant colonial presence. Even the asteroid mining operations of (Insert Company Conglomerate Here)initially relied on hand-drilling and explosives to allow them to break their claims into small enough pieces to transport to planetside processing facilities.
A breakthrough came when it was realized that the lower gravity of moons and dwarf planets would allow for the application of technology rendered essentially useless on full-size planets. Among these technologies were the use of legged and hovering movement systems, and the implementation of modular components. The heavier gravities of Earth and Mars made the joints between components into unacceptable weak spots, and made the energy required to have working legs or hovering bases untenable.
Companies quickly took advantage of this to have a single control pod that could be swapped between tool sets, and chassis systems that could be customized for the terrain and load- from hexapodal systems with gripping feet for work on small asteroids, to light hovercraft that allow for rapid travel on the rough surfaces of low-gravity moons. The tools likewise quickly became more specialized and compact, forgoing material storage and integrated power units to instead siphon the energy required from similarly compartmentalized generator units that could be made for job site efficiency. Soon miners were constructing their own connectors to allow them even more control over the customized setup, and the M.M.V. was born. Miners were able to quickly and easily construct a vehicle to exactly the specifications that the job in question required, and the cost of transporting this equipment was reduced so much that mining the Jovian and Sagan moons became profitable.
From Mining to Military
M.M.V.s were first used in combat during the ill-fated Uprising of Tegid Station. The Europan Miners were eventually crushed by Tegid security forces, but not before a pair of M.M.V.s outfitted with heavy mining drills managed to deal significant damage to many of the structures there, including the main communications tower.
Despite the ultimate failure of the uprising, the amount of damage the M.M.V.s had managed to do meant that they were quickly pressed into service as makeshift combat vehicles by further rebel factions, with slapdash armour added to their stock of parts, and mining explosives jury-rigged into mines and grenades.
As Loyalist security forces began breaking out heavier equipment of their own to combat these new threats, the Miners began constructing the first true weapons to be mounted on their M.M.V.s- crude M.M.V. sized rifles and rocket launchers. Escalation had begun, and the age of the M.A.V. was upon them.