@Foster With fully articulated five-digit hands, responding in real-time to militaristic threats? And bipedal movement? Running on gasoline and internal combustion.
Well, the main driving force behind the R&D of this tech IRL is for prosthetic limbs, and I'm pretty sure we've got pretty lifelike hands and legs right now (plus I just got done discussing Harry Dinsmore's removal of an unexploded mortar-shell that was lodged in a soldier's chest, along with 30% of his uniform and another fella that took a full mag to all his vital bits in 11th Co 3rd Brigade, ROK Marines back in 1967 and went through 14 pints of blood.). The idea of ignoring electronic storage problems by strapping a gasoline generator (or hydraulic pump) on an operators back dates back to the 1960's along with backpack-mounted air-conditioners for troops stationed in SE Asia.
Concurrent development was also for man-amplifying deepwater diving-suits and early space suits, wich again, for ease of use is making
very wholehearted efforts at making responsive 5-fingered hands.
Then there's outright robotics and telepresence units, particularily in respect to "robotic-arms".
The grounds of the complaint isn't the physics, but the touted portability of such a powerful system. -Currently, railguns and coilguns are being pursued for multi-thousand ton craft willing to invest several additional tons into things to power and operate a railgun in order to carry a few more bullets. Not for being mounted to replace tank main armarments.
The break-even point isn't even a nice number like the difference between rifle grenades vs grenade-launchers (which the mass of the launcher including ammo breaks even at around a mere 3 grenades on each system) but more along the lines of several hundred thousand kilograms of ammunition.
For comparison, the ZSU-57-2 only held about 600 kg of shells.