Wow, not much happening in there, Lol. I don’t know of any reason why you would have neutral connected anywhere. Disconnect cable, open the switch box and check. Should only have 3 phase wires and ground actually connected. Remember, if you accidentally swap any of two of the 3 phase wires the motor direction will reverse. Something to watch out for. Would not hurt the motor for short run time in reverse.

Since there us no electrical enclosure on the DC, you will need an enclosure to mount the 3 phase contactor and the remote control.

Not sure if you are interested but it would not be difficult to incorporate auto start on DC. Complexity depends upon how many independent circuits are used by the machines connected to the DC. Each circuit will require a current sense (CS) device. These have a relay that closed on current detection and have a set screw to set activation current to avoid nuisance tripping. Ones I use are around $20 in USA. These devices go around the single current carrying conductor. Apparently some CS devices can go around the full cable but I have no experience with those. I have zero issues using them on the single conductor. The relays in these CS devices are normally open and they can be used to close the relay contacts of the 3 phase contactor. Multiple of these can be connected all together and then to the contactor relay. You have to ensure that the CS relay voltage is compatible with the contactor relay.

Imran