Kaldaien (of Special K mode fame) is working on P4G and already has some tweaks he is testing including:
-a 120 FPS optimized version
-Use of an outside tool (Special K does not distrbute patched executables) to make the game Large Address Aware on 64bit systems. The real fix would be for Atlus to release a 64 bit version of the game instead of this 32bit one.
-some hacks to reduce the amount of motion blur. Apparently eliminating it entirely would be very difficult given how it was coded.
-Other settings to fix framepacing, reduce stutter, etc.
See
this link for what is being worked on.