You are in your game and set up your input settings for /dev/js0... You unplug the joystick, you plug it back in, and suddenly it's /dev/js1, a whole new beast, and you need to remap eveerything. If you could create a dummy js device before the js are initialized, you can maintain a consistency of js0, js1, and so forth, so that games wont be confused if something is unplugged/replugged, and you dynamically map the dummy to the best guess of what it should be. Is this possible?

Part 2: How would you translate that mapping? My idea here is to create a unifying menu for games that can assist with setting inputs at launch. The idea is to change the translation of the real device to the dummy device when switching games, instead of needing to set configuration within the different games.

hm. this happens with cd too, /dev/cd is the virtual device (cd) we use, but actually it is linked to cd0, cd1 or whatever.
probably a similar solution may work in your case too, although you may need some scripting to recognise the device and create the link automatically.