Just my grain of salt from a Mac point of view, if you have ML server installed and more than one Mac up and running - please find faults, it's all "as far as I am aware"... maybe too convoluted for general use!
Mountain Lion Server can create net bootable images, so a nice easy situation sounds like:
0) download your ML install image
1) disconnect from internet, create new ML install, on a USB drive, 16+Gb, minimum install (no languages, print drivers etc)
2) startup from this USB drive, install Bitcoin and wallet (encrypt at your discretion)(you'll have to transfer via USB stock from another machine so as not to connect to internet)
3) use ML server to create netboot image
4) this netboot image is a little like a guest account, and when powered off, will forget everything you installed (so get it right the first time or you'll have to redo everything again!) or did whilst in use - but as your transactions should update on connecting your bitcoin client, then this info is "live" (via internet) each time you boot the image
you can use it as you would a Live CD of Linux, but with everything all ready installed and ready to use, & only perform your "high-end" bitcoin operations from this netboot image,.. if you previously prepared with as high security as possible (firewall blocks everything), you can be pretty sure that your brief use of this image will not be compromised...
* as noted from my member state, i'm a newbie, so if there is something I haven't understood 100% here (about bitcoin), I'm very open to making a better method... ;-)