Honestly, for SAR, I'd outfit myself with mostly military surplus gear. Cheap, durable, designed for not stopping no matter what the conditions.

I'd think seriously about getting a mil poncho and liner and using that as my sleep system. (I actually do use a poncho liner in the summer, I've treated mine with permethrin).

As for rainwear, I guess it depends on the temperatures you are in. I'd skip the rainwear as much as possible. Take a sweater of some sort to put on at breaks.

Do you have specific high vis gear to wear? If not, I'd look at hardware stores for the high visibility orange with scotchlite reflective band mesh vests that road crews wear.