KBD_ZOOM_FOR_MF_USE_MF_KEY is a mistake, likely coming from the original port (and has not been cleaned up).
Thanks for confirming, I've removed it and undefined CAM_USE_ZOOM_FOR_MF
No workaround needed = no need to support CAM_USE_ZOOM_FOR_MF ?
No need for CAM_USE_ZOOM_FOR_MF there, in my opinion. I found the scrollwheel/jogdial the more comfortable way of adjusting focus - a wheel is something that was missing badly on those old Sx IS models.
AFAIK most cams with a jogdial let you adjust MF with it, so if we take this position there's a lot less modern cams where ZOOM_FOR_MF support is needed. I think in recent years most cams that support MF also have a jogdial (though there are probably exceptions)
OTOH, liero asked for it on SX60, which has a jogdial. I think if it worked well, zoom would be more ergonomic than jogdial, since using the jogdial while keeping a one handed grip is a lot harder on most cams. Edit: oops, I forgot SX60 has a front dial, not a normal jogdial....
The jogdial can also be less convenient for big changes: If you hold the key, focus changes more quickly, while with the jogdial you have to spin a lot.