It would be very useful if there will be feature of controlling IS from CHDK menu (not only from script).
One of reasons is described here
http://chdk.setepontos.com/index.php?topic=9421.0 - if bracketing series is done with IS on, each photo is a bit tilted than the other one because of IS mechanism working, even if camera is mounted on tripod.
This affects further image processing (for example HDR) when you need to keep very accurate overlapping one image over another.
If IS control will be available in CHDK menu, it could be sticked to user menu with other settings used when doing HDR series (bracketing EV, mode (AV TV) +/- etc. and IS on/off)