To be entirely fair, it is suction cupped to Jungle Hunter's face in the original and City Hunter's in the sequel. Like yeah he has to remove some hoses and wires but he does still have to yank it off his face. It also didn't entirely make sense for it to be a breather either given JH doesn't show any signs of it being hard to breath, and City Hunter's has his off for longer and takes far more punishment than Jungle Hunter did. And even still if this wasn't an issue to affect his breathing, we have a few on the ship who don't wear masks. And if the environment was fine for them, why isn't it affecting Harrigan? Yeah Harrigan is tired but he just spent all night fighting an alien who can punch through walls like the Kool-aid man.
Though I will agree that while I understand the backpack, it feels a little much. Like for as primitive as Feral is supposed to be, that feels pretty advanced for a guy who has to make use of bones for body armor and food. And kind of odd they'd still use buckles and straps when even Fugitive made use of that and he came from the movie that blatantly uses hard light nano tech space magic.