The development of practical minifacturing omni-tools allows modern militias a great deal of flexibility in equipment load-outs. A vast number of field modification kits, or 'upgrades', are available for common equipment such as weapons, armor, omni-tools, biotic amps, and even grenades.
An upgrade kit typically consists of less than a dozen unique parts and an optical storage disc. When loaded into an omni-tool, the OSD provides all technical specifications required to manufacture the tools and additional parts necessary to install the upgrade onto another piece of equipment. Assembly is typically modular, and installation can be completed in less than a minute.
Since omni-tools are designed to use common battlefield salvage materials such as plastics, ceramics, and light metals (rendered into semi-molten 'omni-gel' for quick use), it is quite possible for a trained soldier carrying upgrade kits to customise gear on the battlefield to fit the current tactical situation.