Per-item fx is planned in the near future according to this log:
http://www.cockos.com/wiki/index.php/ReaperTodo
But there is also another way to accomplish something similar:
1) copy the audio section you want to effect to the clipboard
2) launch a new instance of reaper
3) paste the audio to a track and setup the FX chain you desire on the track
4) save this new project
5) render it, making sure to check "write bwf chunk" & "include project filename in BWF description field"
6) find the rendered wav and paste it into your original project
Now let's say you want to edit the FX settings, just double-click the audio clip and it launches the project that rendered it in a new reaper instance (the project path is in the bwf data)!
This doesn't replace clip FX because:
a) not as quick (though it's faster than you think once you get the hang of it)
b) can't hear the FX in the mix context
But it has its advantages:
a) rendered wav uses no CPU (I guess this depends on how clip FX is implemented though)
b) can do more complex things than simple FX bin, for example layering different tracks