The cart is awesome lemme just say that - normally I need extra batteries, metal, glass, extra wire (and thats the backpack filled up) glass, plasteel, and electrical toolbox filled electronics, not to mention two pipe dispensers and floor tiles / Rglass that I make onsite, to fix any major explosion.
While the engineering cart only saves you a single trip as the sole (working) engineer, it also greatly serves organisation, as you can store half of those goodies on it where they won't be stolen as much or sucked out a breach, or get mixed up with the huge multitude of shit lying around.
Personally I want it to hold power cells, wire, floor tiles and rods, as those are the things I most often have trouble carrying back after fixing something, and what I access most while fixing something, but don't always have room for in my backpack.
Of course we could always use lockers, which hold a fuckton of anything you can physically move, but thats no fun.
Also it would be SUPER FUCKING COOL if it had an automatic pickup function for any glass, metal, rods or floor tiles it rolls over, but I imagine that is something for me to salivate in my sleep over.