If you leave the black wire that normally would connect to the alternator hooked to the alternator and it's also carrying power as it normally would to the ammeter, there will be no load protection on it. If you unhook it and just use the red, the black wire normally going to the alternator would need to be insulated so it doesn't short. The idea behind using both the black and red going thru the connector like the mad diagram is it reduces the amount of current that the pins and wires carry. The one red wire would be carrying all the load of whatever the car needs if you don't use the black at all. Personally I don't think that's a good idea as the pins in the bulkhead connector are part of the issue your trying to avoid. They get hot because they are too small to begin with and cause the connector to melt. A lot of people will remove the red wire and run a heavier gauge wire to the inside of the car and splice into the harness under the dash, this eliminates the lite wire and pins all together, the black wire can be totally taken out of the system doing this also. But you have to drill thru the bulkhead connector or fire wall to run the heavier wire. You'd still need the wire from the alt to the starter relay as you have planned.