"...Robots and Drones from now to the future, and Survival accessories Tents , Freezer boxes, Food Boxes, Ammo Boxes, every thing that a survivor carrys on his vehicle...."
I really like the idea of more "battlefield accessory" type kits - things like stowage, gun emplacements and the other items you mention.
A couple companies (Ertl and Hasagawa seem to come to mind) produced things like that in 1/72 scale back in the '80s and can still find a those sets, but they're way too small, and you can find lots of that sort of thing in 1/35 scale, but it's mostly too big. You can "fudge" the scale a little bit, especially where you're dealing with "heroic" proportions (Death Fields, for example), but there are limits to can be done!
Dreamforge had a (sadly out-of-print) IronCore "Stormtrooper Accessory Set" which was a fantastic product that included things like weapon and ammo boxes, "robot mules", portable computers, tons of loose small-arms (pistols, grenades, anti-tank rockets, SMGs, assault rifles, and more), and all sorts of other fantastic accessories - I bought two boxes of those when they were still available, and I've been using the bits for all kinds of projects for years now. Wargames Atlantic seems to have picked up that license and have been reproducing at least a couple of the other kits in this line, and I really hope this accessory set makes a comeback, too!
Short of that, you do have some great options out there for at least some scenery:
- Mantic Games produced a great little "Sci-Fi Scenery" Terrain Crate in "28mm Heroic" scale (a lot of sci-fi furniture like tables, computer terminals, gun lockers, and so on, as well as ammo boxes, freezers, and that sort of thing)
- Mantic also produces or produced a set of sci-fi doors that might come in handy.
- Mantic also produces some Terrain Crate sets of "modern" terrain that is suitable for zombie apocalypse games, WWII gaming, and other 20th century game settings, in themes like "Haunted Manor", "Gothic Mansion", "Battlefield Ruins", "Cityscape", Campgrounds, "Village Church", "Hospital", "Checkpoint Tango"... all of these things are great for pulp, modern, post-apocalypse, cyberpunk, and even wild-west and Victorian game settings (with a little fudging and curation). The "Checkpoint Tango" set for example includes guard shacks, sandbag walls, and ammo boxes.
- Mantic also produces a lot of fantasy terrain which can be used for historical gaming for pretty much anything from the dark ages, right up to the early 20th century, with some creativity and curation (thinks like wooden crates, barrels, tables and chairs, etc. really don't change a lot from fantasy gaming, through the dark ages up to WWII or so!)
- Archon Studios' "Dungeons & Lasers" products are a great source of sci-fi and fantasy terrain; the main product line is designed to be floors and walls for building 3D fantasy and sci-fi 'dungeons' and cityscapes, but there are accessory sets as well, and the "Sci-Fi Customization Bits" set, for example, is a great source of sci-fi ammo boxes, sentry-guns, robots, computer terminals, and lots of other great terrain, and at least some of the sci-fi and fantasy bits are suitable for 20th-century and near-future gaming.
- Reaper Bones produces some great plastic miniatures in their Chronoscope and Savage Worlds lines (Savage Worlds generally leans toward the Victorian/Western and Pulp era characters, while Chronoscope is a "kitchen sink" of modern and sci-fi figures and terrain); Chronoscope has some great sci-fi military figures ("IMEF" and "Novacorps" factions), as well as a variety of sci-fi, cyberpunk, Jazz-era and Victorian Cthulhu investigators and monsters, etc. (Reaper's bread-and-butter product lines are fantasy figures, which are worth checking out as well for aliens and monsters ranging from Cthulhu style stuff to Gothic Horror regulars like vampires, zombies, werewolves, and the like); Reaper's fantasy Bones miniatures also include scatter terrain and dungeon-dressing that can be useful for historical gaming up to the 20th Century (again, things like barrels, crates, and the like can beused up to about WWII, and maybe beyond)
- Reaper Bones CAV Strike Ops is a mech-warrior sort of war game in a smaller scale than 28mm, but the battlemechs, combat vehicles, and terrain can, with a little creativity, be repurposed as robots and drones
I think we can improv 1/48, 1/56, 1/64, and even the occasional 1/72 or 1/35 scale model kits and accessories (with a little creativity, as these scales are definitely too small or large, respectively, to be convincing if played straight), but there's definitely a problem of keeping scale consistent, considering how spotty the coverage is in these scales.
I think that in 28mm heroic scale, weird scale consistency and proportions just come with the territory - I've come to accept "close enough" as being the standard for this scale; some of the earlier minis this hobby started with are 25mm with more or less normal proportions which put them a little closer to an exaggerated 1/72/HO scale than anything else, while "scale creep" has resulted in some wildly inconsistent results up to a quite exaggerated 35mm or more scale that looks like a weird, cartoonish 1/48 scale, and I think a lot of us just use this stuff side-by-side with a lot of handwaving.
I'd definitely like to see a more consistent and reliable supply of 28mm vehicles, drones and bots, and stowage and accessories, in any event!