I think it's a little risky running that large wire directly from the battery to the controller inside the cab. That wire will have a lot of potiental behind it, both batteries and it's a big wire. A mega fuse or some other type or circuit breaker would be mandatory and careful wiring practices going through the sheetmetal of the cab would be required. And things would still get dicey even if you had a fuse. I bet you need at least a 200 amp fuse to hold it while glowing the plugs.
I know people remote mount their batteries and run large amplifiers with big wires. Even the low rider people run large wires to the back of their cars for all those hydraulic pumps. Just be careful with it.