I would look at the Ranger Rick's Survival Necklace for a basic idea for this type of set-up.

http://www.therangerdigest.com/

M40 has some good ideas on how to modify this kit to make it better.

http://www.m4040.com/Survival/Ranger_Rick_SOS_Necklace.htm

And, you might want to consider a zippered belt to hold the stuff that won't fit around your neck:

http://www.cheaperthandirt.com/BLT501-2753-1965.html

Though really, I would switch to a swim trunk with a zippered cargo pocket, A PSK isn't THAT bulky.

As far as redundancy, yes, it adds weight, but also increases peace of mind. Knives break and get lost. Tents burn down, Sleeping Bags get soaked, etc etc. You have to weigh everything carefully and come to a comfortable compromise between light and fast and having a safety net. Personally, I'll blow a pound or two on a Plan B.