I think that "skin to foil contact" would be the last thing you want. There is nothing magic about a space blanket. First, it doesn't insulate any better than any other plastic sheet.

Secondly there is a marginal extra benefit due to the reflective surface. It reflects back some of the IR radiation that was emitted from your outermost surface (beit clothing or skin) instead of absorbing it. If you are in direct contact with the blanket, any radiative benefits are insignificant compared to direct conduction through the thin plastic.

The main effect of these blankets is aside from shielding you from wind and water is to trap dead air around you. Again, if you are in direct contact with no air gap, that benefit is lost.

Now, I can think of a few excellent uses for these things. First, shiny side up for a desert sun shade. Second, to form the underside of a lean-to to refect the heat of a fire down on you, alieviating some of the crispy on one side, frozen on the other syndrome.