In reply to Calski: Yes you can, I have done exactly this on my G12s albeit for winter boots rather than ski touring boots.
I didn't really fancy trying to drill out the rivets that hold the plastic rear cradle on and so I simply cut the rear cradle off as close as possible to the upright each side leaving a slightly less than 2p coin sized piece still attached. The heel levers, which you can buy online for about £12, then just spring into the holes that are pre drilled for them.
I've used my crampons like this for 3 seasons and never had any problems with either the replacement levers or the pieces I've left still attached. You'll also end up with a bonus spare pair of crampon straps as the levers should come with some.
I've think I've got photos somewhere that I took as I was doing it, or I cold easily take some photos of my crampons as they are now. Message me if you'd like me to dig them out for you
Hope that helps