Hi, just reporting that I was able to successfully map thrust keys to my mouse scroll wheel on arch64 using the evrouter program as outlined here: https://wiki.archlinux.org/index.php/Mouse_buttons#evrouter
Follow the instructions on the arch wiki and remember to logout and login after adding yourself to the input group.
This is my .evrouterrc file:
$ cat .evrouterrc
"USB OPTICAL MOUSE" "/dev/input/event*" any rel/8/1 "XKey/equal"
"USB OPTICAL MOUSE" "/dev/input/event*" any rel/8/-1 "XKey/minus"
Ensure your ship config key mapping in fs2open uses - (minus) and = (equal) to decrease and increase throttle 5% respectively.