If I were making a standard AK with a non reciprocating handle I would make a sleeve that slides over the tube. Attach a handle similar to the G3 so that when unfolded it reaches inside the tube but folded forward it exits the tube. Right behind the gas piston head add a full diameter ring for the lever to act against. Locking stud on the gas block similar to the G3 to retain handle in forward position.
Looking at pics of the INSAS it loooks like they use the external sliding tube, but with a fixed handle? They also use a one piece gasblock/FSB placed way out towards the end of the rifle, the gas piston is longer than a standard AK. With a gas piston ring to interface with the cocking handle it wouldn't need to have a retractable lever to engage it, the travel of the piston wouldn't be enough for the piston head to hit it in recoil if it's spaced right. Stripping is probably accomplished by manually retracting the stud on the cocking handle that engages the piston.