I think the "on a stick" option could work, but I'd also say check what sort of speeds you can expect from the USB before you set up your database - if you're tearing out your hair in frustration because your USB doesn't respond fast enough and your wiki is constantly timing out, it won't be very helpful. (Go USB 3.0 if you can.)

(Also, sorry about the delayed response - I thought I posted this yesterday, yet when I took my morning breakfast break, there it was still sitting unposted. *headdesk*)