I have been doing this already. I use a portable version of Dropbox to sync to the thumbdrive. Inside the Dropbox container I have a portable version of Truecrypt with a passphrase over 25 characters long, a hidden keyfile, and Serpent+AES+Twofish encryption. Within the Truecrypt volume I keep a full copy of the Bitcoin client along with my BTC.

I have 3 of these thumbdrives, one I keep on my person, another is stored in a hidden location at work, and another is stored in a safe with my car title, will, emergency cash, passport, etc.