Gentz was the OCU Redshirt 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 Redshirt 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.
Reniji Sakata was a weak-willed lover of profit, and too timid to stand up for his beliefs.
Reniji cared too little how much he had been spoiling his children (especially Koichi). Reniji, knowing he was grossly outnumbered, didn't dare reveal his suspicions about the methods of his money-making "giants", lest they team up to assassinate him. For a long time, Reniji assumed Koichi was much like his timid father, until that fateful day of learning that Koichi was the Goliath of the Nirvana Institute. Ryuji appearing in the knick of time was apparently Reniji's only hope of boldness to finally stand up for what was right. Koichi Sakata worked for Driscoll and adopted horrifying money-making techniques gladly of his own free will.
Driscoll was nothing more than a convenient opportunity of which Koichi took advantage. By being a despicable influence, Driscoll simply affirmed what Koichi wanted to do; nobody forced anything upon him. Koichi was not bullied into planning the whole 2nd Huffman War nor into murdering his own father for finally taking a stand. It wasn't until he was cornered at gunpoint that Koichi pleaded to not be killed, shifting all the blame to Driscoll, in a desperate attempt to save his own hide.