Da-Rock, as long as it is with friends and they are cool with it, I see no reason to not use it as anything you'd like (within reason, of course).
You could run some allied Eldar jetbikes (the horror!
), you could use them as the various alternate gun-drone profiles (heavy gun drones, for instance- yes, it is a FW model), piranhas are an excellent choice, you could run them as Vespid (I suppose, at least), or heck, you could even write your own rules for them so long as your friends are cool with the profiles. I know there have been some jetbike Tau rules that have come up in the conversion challenges that have been considered by the community. Here's some links to get you started (though I'm sure there are more that can be found)-viewtopic.php?f=1&t=25242&p=317944&hilit=jetbike+tau#p317944viewtopic.php?f=47&t=25249&p=318005&hilit=jetbike+tau#p318005
Please note that there are some modeling things mixed in with rules options, but it should be good to get you started.
So long as your opponents agree to their points/profiles, you should be good to go!
Sweet looking models, btw.
When we forget we are soldiers, we stop fighting.