Charging system

So after looking at a couple of efi systems, I noticed that they all only have a single power inlet. I'm assuming that Chevy leaves the run switch on while cranking whereas these cars do not.
So to simulate that electrically, I'm thinking a couple of 5 Pin relays for fuel injection and the pump I mentioned earlier. 87a would be on the run side of the circuit and 87 would be under start and then just wire the outlets to a single plug so that way they get power regardless of the key position. Accessory is going to be separate obviously. Would I want a diode on one of the pins to prevent back feeding power or is that unnecessary since none of them are in the charging system?
I also feel like using a relay on the coil would be overkill, so just wiring it like stock but with a fuse should be alright?
Would this coil setup continue to work if I changed to an Hei style coil in the future? I already have a pertronix ignitor 2 distributor so I'm pulling power for it from the jumpered ballast resistor.

Last, negative relay switch. I vaguely understand how it works in regards to the neutral safety, fan temp, and horns. Is there any real value in converting the rest of the system to that other then being "safer"