gpg keys on USB drive

[Robert Simmons]

I have been reading up on keeping encryption secret keys on a USB thumb drive 
so that there is an "air gap" so to speak except when the drive is inserted in 
the machine and mounted.

Is it possible to replace all the files in my home directory with symbolic 
links to the corresponding files in the USB drive?  This seems easy, but how 
can I be sure in FreeBSD that the symlinks will always work when the drive is 
plugged in?  I have noticed that the device is sometimes different depending on 
what other USB devices are plugged in and where they are plugged in.

Also, other than the obvious drawback of needing to remember where the drive 
is, and plug it in, are there any drawbacks to keeping keysets such as for 
OpenSSH, geli providers, GnuPG, KWallet, and BitCoin on a USB drive?

Lastly, using geli to create a passphrase based encrypted provider ON the USB 
drive before storing everything on there would increase its security, no?