The return style regulators will help with heat soak and vapor lock issues as well as using an in tank pump will aid in pump life. I'm using an Aeromotive in tank pump as well as an Aeromotive return style regulator mounted on the firewall. This insures the coolest fuel possible going to the carb. Higher pressure EFI can use a regulator mounted at the tank because the higher pressures aren't as prone to vapor lock as the low pressure carbs are.
Be sure you have a fuel pump safety switch wired in to cut the fuel pump in the event of an accident.
Not that Iím the expert, but Iíd suggest the regulator is best positioned when itís closest to the carb or injector fuel rail: Mounted to the firewall as youíve done yours for example. This allows the return to be a low pressure flow rather than if the regulator was in the back which would require the pump to pressurize both the supply line from the tank and nearly all the return. Iíve not seen anyone mount the regulator in the back and mention it only because you commented that it was ok. Iíd suggest regardless of pressure, itís best under the hood and on the firewall or fender depending on space and a bad design if back at the tank/cell.
A discrete kill switch can double as a theft deterrent, and as you mentioned itís important.
Below is a Barry Grant design, this one has two carbs and an external pump, but the idea is there for someone who wants to see/understand a return system.
Summit has this Barry Grant fuel log that can also be used to build a simple return system, just add the return regulator.
One last thought, the pump in the fuel causes the fuel to be warmer than if the pump were external to the tank. Pumps generate heat, no way around that. Pumps in tanks with low fuel levels generate significant heat. So itís not actually the coolest fuel as you commented, itís the coolest pump when inside the tank. Life is a trade off, we have to accept either warmer fuel or potential pump failure from heat. The coolest fuel would likely have an external pump with its own cooling mechanism, maybe a fan or something more exotic.
Anyway, not calling you out on this stuff, just commenting based on my experiences and reading.