The more I think about this game being set in Marathon's world the more bummed I get that more contemporary IP's could have made for a better setting. Take Destiny as the obvious example. An extraction shooter set in the ruined city and wilderness from the very beginning of D2's launch. You've got powerless Guardians, so already we're working with a power level more in line with what fans of the genre might be comfortable with. AI enemies, weapons, and armor could all be drawn from already-existing assets. You want scav runs? Well Destiny has ghost-less normies roughing it in the woods already that you could play as like your Rook. Bosses, raiders, and random events? Destiny has it. Merchants to progress ala Tarkov? Destiny already has it. Seriously, why did this endevour need to cost as much as it did? It is such a ridiculous ROI to hedge on for a genre this niche, so if you're gonna gamble why not draw on your existing game's playerbase, world, engine, and assets?
Moot point since it's not Bungie anymore, but you could have done the same with Halo. Set it during Reach; you're normal ass humans running guns and equipment, most of the same points as above. You can even have that bombed out Euro flavor Tarkov has since Reach has Space Hungarians.