I think a neat thing to have would be the ability to “hotswap” limbs. Sort of like mods for guns, but for separate prosthetic extremities. Like having a right arm with a Fusion Cannon and a mini-flamethrower for killing ghoulies, and another right arm with Hydraulic Muscles and an integrated toolset for welding a shopping cart onto a scooter. Then just change em out whenever you need that special something to get the job done.
Brain-in-jar doesn’t have the mass. The Blob would have to take over the entire system (as in, Blob-in-jar) and would likely have trouble getting used to the controls. The Broken Cyborg has self-repair systems as well as Blob levels, which is why it’s more or less a self-aware zombie.
I like the idea of hotswapping limbs. You could make a combat arm, and a crafting/medical arm, and leave the crafting/medical arm at home, and just go out looting and raiding with your combat arm.
Talking about brain-in-a-jar cyborgs… Am I the only one who wants to make a cephalopod-body-amputee mutant-cyborg named Krang?