You can disconnect the generator but the unit MUST be grounded from the post to the frame and also disconnect the wire to the cutout or the unit will run away and burn up. Thats due to the third brush style of voltage regulation. The cutout IS NOT a regulator! If you run the 6 volt gen with a 12 volt battery, then gen will undercharge the battery unless you move the third brush.
I run my whole car on 12 volts with a starter and alternator to match. Coils dont mind it a bit. ws