Well the main issue here is how crappy Java Webstart is, why not just treat linux users like you do on mac and windows, as mentioned above by delt0r, that is provide a downloadable bundle. Pretty easy to just create an executable batch file (and if needed include your own jre), it worked out pretty well for Tribal Trouble.
You could also just use something like the openSUSE build service which will automatically create packages for all the major distributions.