Yeah, it sounds like a great diorama, and the Panzer Lehr were one of the first things that came to my mind when I saw the photos before reading! The 1/48 aircraft ground crew is a brilliant idea.
The little vehicles and carts and such that those kits include ought to be a lot of fun to work with. I bet you could probably combine them with those "mule" robots from the old Eisenkern command set for some service machines of some sort.
In fact, now that I think of it, I bet some of the plastic battle-mech figures from the Reaper Bones "CAV: Strike Operations" would kit-bash with 1/35 tank workshop accessories to build some heavy welding-bots and such. The CAV mechs are a MUCH smaller scale, making most of them a bit bigger and bulkier than 28mm wargaming figure, while 1/35 tank accessories have a sort of oversized look to them that might look exactly like the sort of thing best suited for heavy machinery to operate by remote control or AI.
Say, somethin like this, carrying a fuel tank (hydraulic fluid tank, lubricant tank, flame-thrower fuel, whatever) on its chassis instead of the cockpit and missiles?
Or, something like this with the gun-arms replaced with welding torches and acetaline tanks?
The great thing about these Reaper Bones figures is that they are cheap (about US $7 a model), the plastic is soft and easy to cut and modify, and the construction is simple (generally not much more than gluing arms, legs, and cockpit onto a torso), and the plastic bonds well with plastic model kit bits and with hard plastic wargaming figure bits, so not much regret on "ruining" the original model by kitbashing it with other bits, and the kitbashing ought to be easy to do!
For some stuff to "bolt" onto these 'bots:
Some accessories from an Italeri 1/35 tank shop equipment set, including a compressor of some sort (I think) and some welding gear, not to mention a hoist that ought to work fine for 1/56 figures, and some hand tools that might be a bit big, but might find some creative use in the hand of a robot or a kitbashed exoskeleton of some sort:
There's also an entire genre of model-building accessories out there for tank ammo (which can probably be fixed to belts of some sort for loading by power-loader into a battlemech to feed its autocannon's ammo addiction):
Much the same thing goes for 1/72 and 1/48 scale aircraft model missiles:
I'm betting it wouldn't be too difficult to mix these sorts of bits together in different ways to make all sorts of maintenance and repair equipment!
In the grimdark future of mech warfare, I kinda imagine portable workshops to salvage these big, heavy, expensive machines probably would arrive with team of specialist mechanics and technicians, supported by swarms of maintenance robots of every imaginable kind....