Well to each his own DrunkCargo. I don't know why and you haven't said why you want to do this but it's your choice.

There is apparently a bicycle route into the airport and presumably you can use that to walk in as well. You can find a bicycle map linked here: Bicycles and Cycling | YVR

So why would anyone want to start walking at 3.30am in -8C weather when they could ride in nice warm public transportation for free?