one reason I'm hesitant to suggest that: when boiled (really boiled, and not just simmered below the boiling temp), all rabbit tends to get tougher and chewier. when I'm stewing rabbit, I'm pretty careful to keep it just simmering (admittedly, tougher/chewier rabbit is fine in small enough pieces in a stew)...and pressure cookers need to get to boiling to get to pressure....
this is why i haven't gone that route, anyway. i suppose if your rabbit burger recipe involves very finely chopped meat, especially if you can marinate it in something somewhat acidic, a pressure cooker could work fine for you. me, i just pick, pick, pick to clean the meat off the bones.