The thing about the 1322 (in my opinion) is how loud it is to pump it. It’s 10 pumps minimum to charge it for 1 shot, and significantly more if you’re going up in caliber. Each pump ends in a loud “clack” that gets louder as pressure builds. You can pump it up ahead of time, so you can have one “quiet” shot, but I found that even new-out-of-the-box mine would lose pressure while hiking for a few hours, and when it came time to shoot the pressure had dropped to a point where poi and poa were very different things. Then, as you reload, the symphony of clacks undoes any of your sneakyness up to that point.
As for modding them, there’s a ton of aftermarket parts out there for them. Pyramid has a bunch... there’s another vendor too that I can’t think of right now.
May I ask what the end goal is you’ve hoping for?