The large mech suits in use by GF marines in “Metroid Prime: Federation Force” were one project in a larger top secret effort by the federation to replicate the tools and weaponry of many bounty hunters (usually without the hunters’ knowledge or consent). The mechs in question were an attempt to replicate Samus’s power suit. Though the mechs performed adequately in some field tests (namely the missions in MPFF) the Samus Aran branch of the project ended up being a miserable failure due to a slew of bad design choices and strained relations between the engineering team and the military commanders who were heading the project. The commanders’ hubris in thinking that they could replicate the power suit was embarrassingly obvious. The project branch was scrapped and the leftovers were salvaged and diverted into two more promising projects.
The engineering team that had been working on the actual build of he mechs was merged with another team that had been working on replicating Ghor’s armorsuit. Up to the point of the merger, the armorsuit team had also been struggling. After the teams were merged, however, they abandoned any pretense of replicating Samus’s or Ghor’s equipment and instead focused on combining what research and designs they had to turn the powersuit mechs into a viable tool for military use. This updated version of the mech sacrificed mobility and anthropomorphic design for tanklike durability and size, packaged in a build much more akin to Ghor’s armorsuit. The mechs were deployed for the first time during the battle of Norion (in MP3) as mobile platforms for anti-air artillery and anti-ground shield generators. They were so successful that they eventually became the primary heavily armored combat vehicles of the GF military.
The research team that had been working on the power suit project was reassigned to use their research on Chozo technology to create more effective weapons. The most promising product of this new program was an experimental lightweight combat suit, packed with advanced weaponry and designed for use by commando style troops. The suit was almost ready to begin field tests… until the lab was destroyed and the single prototype stolen… by Sylux. The GF scrapped the project and erased all mentions of its existence from the records.