That’s sure possible. New track friction component doesn’t require a suspension anymore and can use collision information. Which means that tracks as on heavy construction machinery (with little to no suspension) can be simulated.
The arm can be done with physics constraints, but it will take quite some time to tweak every joint and mass of part to make it look stable. Better results could be achieved with PhysX Articulations: Articulations — NVIDIA PhysX SDK 3.4.0 Documentation
but its not exposed in UE4. Potentially, it can be added with c++ code.