Nothing wrong with scratch-building that sort of stuff - I do it all the time - and I could even recommend some 1/48 kits that were probably aimed at WWII modelers that supply a great variety of tools, barrels, boxes, bottles, and other assorted bitz that make excellent stowage or diorama details, which could probably be used just as well for most of the 19th and 20th century and general pulp, post-apocalyptic, steampunk, and Quar/Death Fields purposes, as well as fantasy gaming, and still find a foothold in a lot of other historical and sci-fi settings as well.
But, if there's a market for it - and there certainly seems to be a niche market for generic stowage - why not a WA "Death Fields" stowage and vehicle modification kit with a frame of that sort of stuff, now that we're starting to see vehicles in the Quar and Death Fields lines, and in the Digital catalogue?
There's a limit to the appeal for things like generic jerry-cans, spare tires, bolt-on armor, or weapon mounts, but they're useful enough and you can get a little more mileage from including assortments of ammo crates, rolled tarps, tools (shovels, axes, sledges, etc.), and random vague shapes under tarps. Fill remaining space with spikes, skulls, and other gothic grimdark greeblies, and you probably won't be historically accurate for a Bronze Age tank or truck, but you do have stuff that would work fine for spiffing up a fantasy wagon/cart/scatter-terrain, and a little something for almost any vehicle you would want to modify from the Quar, Death Fields, Last War, pulp, steampunk, post-apocalypse, and broad-strokes general-purpose historical gaming (especially world war, Victorian, Napoleonic, and similar settings.)
That said, it looks/sounds like the upcoming terrain sets for the Baron's War and Death Fields might be prepared to cover a lot of this sort of territory. For example, with perhaps a little modification, those Baron's War scatter terrain bits - barrels, crates, and so on - could surely be mounted to the flat-bed version of the Damned vehicle, and would look perfect there as supplies or plunder.