I found this while searching on google. I haven't tested this as I don't have a need, but you can be our beta tester
It seems you can achieve this by modifying your XF86Config or x.org.conf file in such a way:
Option "Device" "/dev/js0"
From my take on this, you could insert this into your XF86Config or x.org.conf file and where it say's Driver "joystick" change this to "sidewinder" and perhaps that would put the sidewinder on /dev/js0 maybe.
I'm not really liking the way that works, but I was also thinking that during the module loading that perhaps you can assign the device. Maybe something like modprobe sidewinder /dev/js0 or something along those lines. You can also have it read from /etc/modules.conf.
I have a joystick myself so I'll practice with somethings and see what I come up with, but I can't promise anything because it's not working in Linux atm. I can't even get my kernel to see my joystick.