Co-Op hack update
and updated game notes
(thanks to SubDrag for some of the notes somewhere in there). The latter link has some folders holding the source and binary of the ridiculous codes I've posted earlier.
Oh, also, thanks to SubDrag I have JFG running in Nemu. This is what he had me do:
Courtesy of SubDrag; open nemu64.ini in your Nemu emulator folder and change the JET FORCE GEMINI settings to these to get the game working:
[Jet Force Gemini]
FriendlyName=Jet Force Gemini
Comment=T | Fully Playable - Uses FB
As you should see the default compiler mode Nemu has for the game is 5, which apparently causes problems.