You seem to have the idea.
Propane boils at -42.09 °C, close enough to - 40°F that it does not matter. This means that below -40°F it stays liquid instead of giving you any gas to burn.

Even at 0°F we usually need preheaters to make sure there is enough pressure for heaters to work right. As the gas comes out of the tank the expansion causes the temperature to drop even more and it drops the pressure.
Have you ever noticed the frost buildup on propane tanks being used in cold weather?

As the temperature rises the pressure increases.
At regular temperatures you need something as strong as a propane cylinder to hold it because the pressure is so high.
Butane you can buy in a light weight tin can.
Butane and isobutane are trade offs of the fuel efficiency for the weight of the container.
By mixing a bit of propane with the butane you get some of the pressure of the propane, but it averages with the vapor pressure of the butane so it is still not really high pressure at normal temperatures.

So if you want really low temperature fuel you would need a lighter built heavy enough to handle the higher pressures at normal temperatures.

This basically means you have to warm your lighter up if it is cold out. Stick it in your pocket, tuck it under your armpit, or hold it in your hand for two minutes.
Whatever it takes to warm the fuel up enough to give enough pressure for it to work.