The biggest bottlenecks are hardware design and software design. Materials science to an extent, particularly battery materials, but we could build robots with

The biggest bottlenecks are hardware design and software design. Materials science to an extent, particularly battery materials, but we could build robots with currently-available materials and power density if only we knew how to make them work usefully enough. I'm not against the concept and I agree the manufacturing can be scaled. There just isn't a product yet.