It is not an ignition switch, unless you have hidden an IC engine somewhere, its a 48V isolator. There seem to be a shortage of fuses in your block diagram. Contactors have a low contact volt drop, but a finite life and significant driving power, auxillary contacts can be fitted too provide further functions easily. Power semiconductors need to be heatsinked and are prone to over voltage spikes, low driving power do not wear out.
I would have fed the 48V batteries to the isolator via a 100A fuse then straight into the converter/motor driver. From the isolator feed via a 5 A fuse to the control gear via an " ignition switch". Control the inverter via the micro.
Frank