Feinting. I'd say open-glove control techniques, but they're generally punished much quicker in the amateurs. If your guys aren't amateurs, then I'd say open-glove control.
Another thing I'd say is changing the tempo. A lot of amateurs will paw a bit and let every punch go as fast as possible; Khan has done this all of his pro career too. Bhop and Wlad are two boxers that spring to mind who change the tempo well. Will be awesome if you can get videos of you doing the drills with the boxers, would be interesting
feinting is good, its a lost art good call Jdsm. Body punching seems to be absent in todays amateurs partially because of the scoring system. Head movement is another area that should be worked more and more but gets neglected
A night on body punching. Where the feet should be, movements/combinations to set it up, combinations to follow up, defence while attacking the body, defending your own body. As mentioned before, body punching really is overlooked in the amateurs but shouldn't be neglected in training.
Proprioceptive awareness, makes everything work. sharpens things up as far as nueromuscular response, and posture. Theres numerous adaptions to it, like one leg squats, its fun. If its too hard, put cotton wool in there ears , true.
have them do 4min rounds (each round divided into 4-1min skill segments) where they use the last skills to build on the next. when they are either shadowboxing or hitting the bag have them do the first minute is only feet and headmovement, then add the jab, then add the straight power and the final minute is adding short shots. they'll learn how footwork sets the jab, which sets the power, that sets the hooks and uppercuts.
On-line I watch a ton of video of people sparring and in amateur bouts... So I would suggest teaching how to throw a proper left hook and how to go about landing it. You don't see much of that and, if you are going to grow into a KO puncher, odds are it will be your left hook that gets you there. Teach how to integrate your offense and defense. There is a whole lot of "you take your turn, I'll take mine" out there. Incorporate offense and defense into a seamless thing that begins with making the other guys miss. My belief is that this requires a giant step away from the post-Tyson school of thought of "move your head constantly" to a purposeful school of thought. Tell me what you think/learn. Best wishes my friend.