magnetic latch relays for high current charge applications are mature and cheap technology (pretty standard in marine battery charging solutions). it would be simple to engineer a reliable solution that connects / disconnects the appropriate connector off a simple 12v signal wire using nothing but off the shelf retail parts.
Here is a marine version intended for 12-24v 500A applications, but rated for up to 700V. It retails for around $300
https://www.bluesea.com/products/76...rging_Relay_with_Manual_Control_-_12V_DC_500A
this would be a drop in ready off the shelf part for $300 (retail) that could be used to turn on & off the different cables coming out of the charger. I'm sure you could buy them in bulk for a LOT cheaper