Front Mission/WMG

Gentz was the OCU Red Shirt from the game's first mission.
Neither of them really had a narrative purpose. OK, maybe Gentz did, but the Canyon Crows could have just as easily extrapolated the location of the Nirvana Institute from Frederick communicating with a faceless leader of the Spirit of Huffman. If this theory is applied, however, we could easily extrapolate that Gentz learned the truth about Larcus earlier than Royd did - despite being disavowed for the same fiasco, he could've been transferred to a border team on the Mail River and worked his way eastward.

Jean is an ancestor/descendant of fellow Red Shirt Gene from Mobile Suit Gundam.
Again, no real narrative purpose except to maintain that the bad guys aren't so different from the protagonists by having them face named grunts instead of additional Mooks.

Mary/Maury is the female alternate-universe version of Drachma.
They each hate the player in the beginning, lost their family in a tragedy, and named their vehicle of choice after their dead son.
 * Strange, I always assumed she was just a big Queen fan.

The Gun Hazard universe is a possible premature offshoot of Super Robot Wars's "Shadow Mirror" universe.
Had the Society succeeded in bringing never-ending war upon the Earth, they would have flourished well into the age of larger mobile weapons and brought their well-intended extremism to other realities.
 * There's also a good chance the Controller is a way-past-his-prime Vindel Mauser. Or Davros.

Genoce survived.
Some possibilities for his current whereabouts:
 * After crashing on the foot of Atlas, he stumbled out and swam to shore...that is, the shore of Huffman Island, where he started the "Spirit of Huffman" as Gentz.
 * His body got liquified in the fall, but top scientists at Kernelight managed to convert the remaining body tissue into a multifunctional membrane. He currently roams the Dragon Quest Heroes universe as Slival.
 * He sent his Wanzer down empty and absorbed the remaining energy of Atlas's core into himself, becoming the governing AI hellbent on preventing the weapons mounted within from being used in another meaningless war.